Some years back I saw the problem brewing on my own server, dug into Mastodon’s code, and wrote a hacky shell script to cull accounts older than 3 months on my server. I shared it, and it’s used all over the fediverse for the same thing. Only just recently has there been movement to put the feature into Mastodon and not by the maintainers. Chances are if you’ve been here a while some random instance you’ve never seen has all your posts, images, etc. and can’t delete them. Holy GDPR, Batman!