Consciousness in MN 49 DN 11 is wrong translation (Brahmanimantanikasutta, Kevaṭṭasutta)

Related answer: https://unmixedtheravada.blogspot.com/2019/01/rebirth-appears-in-both-sutta-and.html

Pre-knowledge:

Jānāmi means I know.
Vijānāmi means I know various things.
Viññāṇa is noun from Vi prefix+Ñā root+Yu suffix.
Vijānāmi is verb from Vi prefix+Ñā root+Na suffix+Mi Case-endings.
Vijānāmi term is same as "I do Viññāṇa".
Viññāṇa = Vijāṅa = Cognition Of Various Object.
Recite and learn kaccayaṇa-vyākaraṇa from the Tipitaka Memorizer for more explanation.

Question 1

What is the invisible consciousness or consciousness without >surface described in MN 49 and DN 11?
Is it a cosmic consciousness like the one found in Hinduism? I guess not.

1. It definitely isn't cosmic consciousness. Actually, it is like cognized/cognition in the other Sutta. However to understand it, the reader must recite and memorize Pali, first, then learn it with the inherited Tipitaka Memorizer, such as Pa-Auk because the proficiency is definitely required to understand the whole detail of each sutta. Even you can read Pali, Atthakathā, or ṭīkā, the proficiency still required.
   See below explanation to understand why I tell you like that.
2. Your quoted MN 49 Brahmanimantanikasutta is bad cut, and wrong translation. It is:
   Buddha said Brahma think this is the all cognizable thing which could be cognized by his consciousness:
   

   ‘A galaxy extends a thousand times as far
   ‘Yāvatā candimasūriyā,

   Buddha claims Buddha cognizes more than Brahma:
   

   But there is another realm that you don’t know or see.
   Atthi kho, brahme, añño kāyo, taṃ tvaṃ na jānāsi na passasi;
   But I know it and see it.
   tamahaṃ jānāmi passāmi.

   Buddha claims Buddha cognizes Radiant Brahma:
   

   the gods of streaming radiance …
   ābhassare kho ahaṃ, brahme … pe …
   the gods replete with glory (than above brahma) …
   subhakiṇhe kho ahaṃ, brahme …

   Buddha claims Buddha cognizes Nibbāna:
   

   Having directly known earth as earth, and having directly known that which does not fall within the scope of experience based on earth, I did not identify with earth, I did not identify regarding earth, I did not identify as earth, I did not identify ‘earth is mine’, I did not enjoy earth.
   Pathaviṃ kho ahaṃ, brahme, pathavito abhiññāya yāvatā pathaviyā pathavattena ananubhūtaṃ tadabhiññāya pathaviṃ nāpahosiṃ, pathaviyā nāpahosiṃ, pathavito nāpahosiṃ, pathaviṃ meti nāpahosiṃ, pathaviṃ nābhivadiṃ.

   You can see that the contexts force to translate "viññāṇa" as "nibbāṇa".
   2.1. Below quote, Brahma is asking for "the thing" which is not within the scope of experience based on all (no one has known before, including this brahma) but viññāṇa (consciousness) is within the scope, so viññāṇa must is translated as adjective complement of "the thing (nibbāna) which is not within the scope of experience based on all" in above paragraph of it.
   2.2. Brahma acts like he has the best cognition, so the Buddha shows him what he never cognizes before, nibbāna which is cognizable, invisible, infinite, radiant all round below.
   2.3. You can see below translation has many words appearing in above quotes.
   2.4. "Viññāṇaṃ, anidassanaṃ, anantaṃ sabbato pabhaṃ" all are adjective complements, but the previous translation is a noun, so I wrote above "the translation is wrong". Viññāṇaṃ in this context is cognizable (adjective complement of the nibbāna noun), not consciousness (noun).
   2.5. Buddha claims the best cognizable thing is Nibbāna below quote.
   

   ‘Well, good sir, if you have directly known (the thing) which is not within the scope of experience based on all, may your words of (the thing) not turn out to be void and hollow! (Don't just say you know (the thing) because everybody can "say I know (the thing)" but they may don't really know anything! Describe it if it really is a true story!)
   ‘Sace kho, mārisa, sabbassa sabbattena ananubhūtaṃ, tadabhiññāya mā heva te rittakameva ahosi, tucchakameva ahosīti.
   (The thing[=nibbāna]) that is cognizable, invisible, infinite, radiant all round (nibbāna is invisible but similar to have radiant all round more than all Brahma-deva which appeared in many paragraphs above)—that’s what is not within the scope of experience based on earth, water, fire, air, creatures, gods, the Creator, Brahmā, the gods of streaming radiance, the gods replete with glory, the gods of abundant fruit, the Overlord, and the all.
   Viññāṇaṃ anidassanaṃ anantaṃ sabbato pabhaṃ, taṃ pathaviyā pathavattena ananubhūtaṃ, āpassa āpattena ananubhūtaṃ, tejassa tejattena ananubhūtaṃ, vāyassa vāyattena ananubhūtaṃ, bhūtānaṃ bhūtattena ananubhūtaṃ, devānaṃ devattena ananubhūtaṃ, pajāpatissa pajāpatittena ananubhūtaṃ, brahmānaṃ brahmattena ananubhūtaṃ, ābhassarānaṃ ābhassarattena ananubhūtaṃ, subhakiṇhānaṃ subhakiṇhattena ananubhūtaṃ, vehapphalānaṃ vehapphalattena ananubhūtaṃ, abhibhussa abhibhuttena ananubhūtaṃ, sabbassa sabbattena ananubhūtaṃ.

   Abhidhamma and Atthakathā comment some same thing to me: Nibbāna is cognizable and invisible. Visible thing has the end (paritta, little) but nibbāna is invisible (endless, ananta). "Radiant all round" is just the similitude that nibbāna is the best of the overall radiance.
3. The part of DN 11 Kevaṭṭasutta is the same case of above, MN 49 Brahmanimantanikasutta. It just added the rhetoric of "viññāṇa".
   A bhikkhu try to cognize the cessation of the Four Element, but the great Brahma says he doesn't know but the Buddha knows it:
   

   But I too do not know where these four primary elements cease with nothing left over.
   Ahampi kho, bhikkhu, na jānāmi yatthime cattāro mahābhūtā aparisesā nirujjhanti, seyyathidaṃ—pathavīdhātu āpodhātu tejodhātu vāyodhātūti.

   That bhikkhu's question is "where is Four Elements ceased?", so the answer should be the cessation state, Nirodha (nibbāna). Nibbāna is where the Four Elements ceased, where is cognizable, and where is invisible.
   So, it is the same case of above, MN 49, Buddha claims the best cognizable thing is Nibbāna below quote.
   

   This is how the question should be asked:
   Evañca kho eso, bhikkhu, pañho pucchitabbo:
   

   “Where do water and earth,
   ‘Kattha āpo ca pathavī,
   fire and air find no footing;
   tejo vāyo na gādhati;
   where do long and short,
   Kattha dīghañca rassañca,
   fine and coarse, beautiful and ugly;
   aṇuṃ thūlaṃ subhāsubhaṃ;
   where do mentality and matterity
   Kattha nāmañca rūpañca,
   cease with nothing left over?”
   asesaṃ uparujjhatī’ti.

   And the answer to that is:
   Tatra veyyākaraṇaṃ bhavati:
   

   Where is cognizable, invisible,
   ‘Viññāṇaṃ anidassanaṃ,
   infinite, radiant all round.
   anantaṃ sabbatopabhaṃ;
   Here’s where water and earth,
   Ettha āpo ca pathavī,
   fire and air find no footing;
   tejo vāyo na gādhati.
   here’s where long and short,
   Ettha dīghañca rassañca,
   fine and coarse, beautiful and ugly;
   aṇuṃ thūlaṃ subhāsubhaṃ;

   This is the additional more than DN 11, the rhetoric of "viññāṇa".
   Because Buddha uses Viññāṇa as an adjective complement of nibbāna, above, but Buddha uses Viññāṇa again below quote from DN 11 as a noun, which is ceased by nibbāna in the cessation of dependent origination.
   

   here’s where mentality and matterity
   Ettha nāmañca rūpañca,
   cease with nothing left over—
   asesaṃ uparujjhati;
   with the cessation (nirodha,nibbāna) of consciousness (viññāṇa),
   Viññāṇassa nirodhena,
   that’s where this ceases.”’”
   etthetaṃ uparujjhatī’”ti.

4. It is important to understand MN 1 mūlapariyāyasuttaṃ with its commentary first before reading MN 49.

Question 2:

This answer implies that this invisible consciousness or consciousness without surface is the re-linking consciousness (patisandhi-viññana) that connects one lifetime to the next. This also implies that the re-linking consciousness (patisandhi-viññana) which is the invisible consciousness or consciousness without surface (viññāṇaṃ anidassanaṃ) is the consciousness that descends into the womb causing materiality-mentality (nāmarūpa) to arise (from DN 15). Is this right?

As I described DN 11 above, the first Viññāṇa is an adjective complement of nibbāna, but the second Viññāṇa is noun, which is ceased by nibbāna.
Therefore, the first Viññāṇa in DN 11 is Nibbāna, not re-linking consciousness. The second Viññāṇa is cresed re-linking consciousness by nirodha (nibbāna), not nibbāna.

Question 3:

Also, the description of "invisible, infinite and radiant all round" sounds very similar to the "luminous mind" (pabhassara citta) from AN 1.51-52. The same word "pabham" (luminosity) or "pabhassara" (luminous) is used in both MN 49 and AN 1.51-52. How is the invisible consciousness or consciousness without surface related to the luminous mind?

It definitely is different, just a bit of it refer to each other.
It is Nibbāna, not luminous mind. I already described in above MN 49:

(The thing[=nibbāna]) that is cognizable, invisible, infinite, radiant all round (nibbāna is invisible but similar to have radiant all round more than all Brahma-deva which appeared in many paragraphs above)

"Radiant all round" is just the similitude that nibbāna is the best of the overall radiance of below:

Buddha claims in MN 49 Buddha cognizes Radiant Brahma:

the gods of streaming radiance …
ābhassare kho ahaṃ, brahme … pe …
the gods replete with glory (than above brahma) …
subhakiṇhe kho ahaṃ, brahme …

Pabhassara Citta in AN 5.23 is wholesome mind, not nibbāna.

In the same way, there are these five corruptions of the mind. When the mind is corrupted by these it’s not pliable, workable, or radiant. It’s brittle, and not completely immersed in samādhi for the ending of defilements.
Evamevaṃ kho, bhikkhave, pañcime cittassa upakkilesā, yehi upakkilesehi upakkiliṭṭhaṃ cittaṃ na ceva mudu hoti na ca kammaniyaṃ na ca pabhassaraṃ pabhaṅgu ca na ca sammā samādhiyati āsavānaṃ khayāya.
What five?
Katame pañca?
Sensual desire, ill will, dullness and drowsiness, restlessness and remorse, and doubt.
Kāmacchando, byāpādo, thinamiddhaṃ, uddhaccakukkuccaṃ, vicikicchā—

Pabhassara Citta of AN1.41-48 are the same, but Pabhassara Citta of AN1.49-50 is different because the contexts are not talking about the wholesome or unwholesome mental factors of current arising mind (AN 5.23), but AN1.49-50 talk about normal mind, bhavaṅga (the factor of keeping current becoming). It is sleeping mind, which looks like dirty when the unwholesome mental factors, external defilements, arising instead. We cannot do unwholesome or unwholesome karma while we sleep, so before the defilement mind factors arise instead, that slēping mind looks like effulgent.

49. Bhikkhus, the mind is effulgent, it is defiled by external defilements.
50. Bhikkhus. the mind is effulgent, when released from external defilelment.

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The answer is very clear for me, but it can make the reader confuse because of many references, many pali term, many words referring to each other, and my English skill lacking. That's why I wrote:

However to understand it, the reader must recite and memorize Pali, first, then learn it with the inherited Tipitaka Memorizer, such as Pa-Auk because the proficiency is definitely required to understand the whole detail of each sutta. Even you can read Pali, Atthakathā, or ṭīkā, the proficiency still required.