What's the difference between a "teaching" account and a normal one? Is the only difference that a teaching account allows audio input?

Yes, that is the only difference.

I've considered changing this. Bandwidth is cheaper than it used to be. Perhaps later I'll give all KGS Plus accounts audio capability. We'll have to see.

Ooh, yeah. Another reason to try harder to keep my KGS Plus account up-to-date.

I don't teach (online) often enough to ask for a teaching account just to get the audio, but I would probably teach online more often if I had the audio (because I type too slow -- I don't like to teach online).

The teaching account also has a better moderate feature (being able to filter things in quiet mode).