Okay, I think I see the problem here, and its actually personal, in and of I'm not as familiar with the events of AtlA as most of us are. Of course, in your usual, unflappable style, thats okay, as I'm easily able to get the gist of the tension between this Katara and Azula, just not quite some of the specifics.

In specific, the specifics that prompt the punchline about Bitches and Tyrants. Can anyone point me at something to educate myself better?

Do like that you've decided that past Avatars can qualify for Vallhalla just as much as anyone else, for some reason I was thinking that they kinda mostly had to hang in the spirit world of Diqu in case the current avatar needs a consult, etc. Now it sounds almost more like they could hang there if they so desired, but a lot of them dont and just hurry back and meet the avatar there if so needed.