if you have a transparent gif avatar and update your avatar, then go back and scroll down in the notifications, your avatar disappears on your end and is replaced with a blank space
oh also if you have a gif avatar(? might just be *any avatar*) and update it, then go back in history, mastodon freaks out and can't figure out if you have the old avatar or the new one
it's fixed if you post, but for that time you're just Out For Lunch