Skill Comparison?

How would you describe someone with Artes LIberales score at 16? What kind of things would they be able to do as mundanes, as magi?

Mundane: One of the most skilled academics to have ever lived, based on a gauge that such a person could write a level-8 summa. At the same time, it should be noted that sources for learning high levels in Artes Liberales and Philosophiae are far more abundant than are sources for most other things, so getting scores in the double-digits is not unreasonable at all. So I would not consider a score around 10 to be so incredibly good as a score around 10 would be for something like Single Weapon. Also, using this to align things (can't remember what it's called from A&A) to get bonuses of +3 to other things should be relatively trivial. Finally, such a person is probably literate in every language they'll ever learn.

Learned Magicians: As the mundane, plus an awesome bonus to lab totals as this is their version of Magic Theory. This should also mean they can customize their labs well.

Magi: As the mundane, plus fantastic at ceremonial/ritual magic. I find this is more important for ceremonial magic, though, since ritual magic doesn't have the divisor. That Artes Liberales score alone nearly accounts for two full magnitudes of a spontaneous spell for any TeFo combination the magus desires.

Cautious with AL is great for ceremonial magic.

Astrological and mathematical mysteries also benefit from AL (and cw:AL). Regular alchemists do too.

If you want to read almost any manuscript ever written, AL 16 is the bomb, though it won't provide access to lost alphabets.

Some sahirs love their AL.

This is what reputations are for. If the person has been active in scholarly circles for decades, publishing works and engaging in discourse, they probably have a reputation score of 3 or 4. As such, they will be recognised throughout academic circles and people will probably seek them out. Note that this should be covered by their social status virtue. Magi with a high score might be completely unknown; not all magi publish regularly.

If the person hasn't been active and has no reputation, the score in the ability isn't going to mean anything in terms of how they get treated. Because no-one knows they're talented.

It's the same with magi and arts. A magus might have 30s in a few arts but have absolutely no reputation if they haven't done anything of note with those arts. Another magus might have 17s in the same arts and be known as a 'master' of those arts because they've published texts, given seminars, debated with their fellows, etc.

Repeatedly demonstrating incredible ability is probably going to result in a reputation being gained over time.

Alternatively, if the person is not famous for his ability because he never displayed his knowledge (through books or teaching class or debate), he might be known as a famous collector: he must have spent a lot of money to gather enough tractatus to bring him to this level of knowledge !

Assuming that from level 6 onwards he learned almost exclusively through tractatus, that's about 575 xp, so counting an average quality of 10-12 (considering the topic is popular amongst mundane scholar, it is reasonable to assume good quality tractatus are available), that's about 50 tractatus of fine quality.

There are probably some high quality tractatus amongst them, so unless he took special care not to be identified as the buyer/copyist, he should be know for his collection.