Which makes this whole example that obviously tailored to prove a single point, that it shows its own irrelevance instead.

One Shot:ezzelino:
Also, I'm not really sure why "prolific" would apply to the Quality of books one writes; prolific is about quantity, not quality.
Not quite. It is best explained as 'fruitful' to non-native speakers, and can mean both together.
No. I'm sure that, being well versed in English as well as Latin, you realize that prolific is narrower than fruitful, in that it precisely lacks the connotation of good quality.
In the combination "prolific author" it mandates the quality needed to make other people want to read the works. (A "prolific poster to RPG forums" need however not be an author at all.)

One Shot:ezzelino:
So, to reiterate: there are other ways one could achieve a Quality of 15 on a Tractatus, but by RAW Mythic Communication is not one of them.
There is no unique RAW reading for this - as for so many things in ArM5. In every campaign where it comes up Mythic Communication: prolific author needs to be discussed and decided by the troupe. And there are also clear statements by ArM5 authors that this is the way they intend the rules to be used.
Ah, this is interesting. Could you give a quick pointer to these clear statements?
Have a look here for example: New Herbam (and other) Spells , especially its ending is quite categorical:
... but even in this last sentence you seem to be suggesting that groups could previously play in a sort of "pure" way advocated by some D&D players, where it's all by the book and only by the book. Ars has never worked that way. Never. It has always been about your choices, expressed through your play contract. That's why when there are disputes we say "Ask your troupe" not "Ask your GM". The rules have never been the one proper way to play, they've always been a guide to negotiation of play.
Cheers