TIL:
If you send out a meeting invite to a mail list, clicking on the '"Yes" or "No" I will attend' button tries to add the mail list (not you, the mail list recipient) to the meeting, which generally errors out.
If you plan on attending a meeting that's being held a month ago, and you are part of a mail list that got an invite. DO NOT ASSUME CLICKING "YES" MEANS THAT YOU GET A CALENDAR REMINDER! You gotta do that manually, it turns out.
Gmail + Gcalendar is very clever, that way.