Have to know before to read atthakathā

Tipiṭaka and atthakathā are keep by oral study system. So:

1. There are uncountable descriptions that atthakathā described in previous atthakathā and in visuddhimagga, so this atthakathā is not complete. This is the problem of reading study system, but is not a problem of reciting study system which is ancient method.
2. Original text in pāli-language is the best, easiest, and maximum performance way to learn tipiṭaka and atthakathā. The translation is just an alternative way.
3. Tipitaka-memorizer is very important qualification to be a teacher in atthakathā culture.
4. Each sutta and it's explanation must complete in itself, by the relation of words/sentence/paragraph. And they must be compatible with the other sutta by meaning.
• So, mostly atthakathā are not comment or opinion, but it is description. Because atthakathā describing the reference to prove the relation of each word in tipitaka. Mostly words of atthakathā has it's own reference from it's sutta context or the other sutta which is relating. Then sariputta and the other tipitaka memorizers use these relations to author their own canons, such as khuddakapātha, paṭisambhidāmagga, niddesa, abhidhamma, parivāra, netti, commentary, etc. In contrast, mostly comment or opinion words base on concepts, which mostly without reference.  So, mostly explanations in atthakathā are not just the comment, but it is the description.
5. Atthkathā-teachers are very serious to keep tipiṭaka as original. Changing anything in tipitaka is seriously denied by tipitaka and atthakathā.
6. There are 4 ages of atthakathā: 
1. 1st-saṅgāyanā-atthakathā (0BE), 
2. 2nd-3rd-saṅgāyanā-atthakathā (~100BE, ~218BE), 
3. siṅhala-atthakathā (450BE-900BE), modern-atthakathā (~950BE). 
4. The modern-atthakathā. This is the combined version of the other atthakathās, so nowadays just modern-atthakathā still available. But we can say the other atthakathās still going on in modern-atthakathā, because the modern-atthakathā composer, buddhaghosa,  swore to the mahāvihāra-saṅgha that he must did just translating and merging all atthakathā together. This swearing still appear in the introduction of every modern-atthakathā.
7. Modern-atthakathā were categorized very clear. The 1st-saṅgāyanā-atthakathā is the primary structure. When something in the other atthakathā is difference from the primary structure, it is added next to it with note mark, if is necessary, as an extension, such as "in pañcarī (siṅhala-atthakathā) wrote...", then the structure return to the primary structure again. Buddhaghosa's opinions are the same. So no any complication between each age of atthakathās that were combined in the modern-atthakathās.
8. Reading study system doesn't has good enough performance to understand tipiṭaka and atthakathā. Many misunderstanding in tipiṭaka and atthakathā come from reading. Because reading through often cross many syllable/word/sentence/paragraph/sutta/vagga/etc, but reciting is harder to cross.