In a community in which texts had a constitutive importance and only a few people were literate, it was inevitable that those who were able to explicate texts would acquire authority for that reason alone (Books and Readers, 9-10).Moreover, as I have argued here (Orality and Literacy V: Illiterate Tradents), it is not just a question of taking literate authors of literary texts seriously. It is also a question of focusing on literate tradents. The idea of illiterate early Christian tradents remains problematic. Most of the tradents we know about were literate, and one of the earliest pieces of known tradition (1 Cor. 15.3-5) presupposes literate tradents and the importance of tradition interacting with what is written.
Now in that post, I did promise a note on Acts 4.13, where Peter and John are described as ἀγράμματοι, sometimes translated as "illiterate". Many commentators suggest that the word is more appropriately translated "uneducated" than "illiterate", not least because the same text, Acts, depicts Peter as quoting extensively, verbatim, from the Hebrew Bible (or perhaps more accurately here in Acts, the Septuagint). I make no presumption of historicity since it seems likely that Luke has composed those speeches; the point is that the author who depicts Peter and John as ἀγράμματοι in the same text also has them quoting their Scriptures verbatim. Therefore the likely meaning of the word, as Luke uses it, is "uneducated" and not "illiterate", and this verse does not provide a one-stop response to arguments in favour of the likelihood of literate tradents.