If at some point you want to delete your account and have your posts and comments be gone, you better delete it all manually before you actually delete the account, because that deletion process does not really work as advertised.
For my main account on world (which runs an outdated lemmy version), it seemed like at least the account deletion was federated so that my user page was no longer browsable from other instances, but none of my posts, comments or images had been deleted, not even on the home instance.
The homie @MrKaplan@lemmy.world helped me by manually deleting my stuff, but it seems like that has only worked for the home instance, posts and comments seem to still be readable from other instances (except for some of the images that MrKaplan manually deleted too, but that was only possible up to a date not too far in the past because lemmy used to not associate user uploads with the accounts). So my old posts from the world account can be viewed just fine from other instances:
For other instances that are more up to date the process is even worse imo, while locally things seem to get deleted, federation does not seem to happen at all. For example you can still browse my deleted slrpnk or lemmee accounts from other instances just fine:
https://slrpnk.net/u/achtungdrempels@lemm.ee
https://lemm.ee/u/AchtungDrempels@slrpnk.net
Account deletion in piefed works kinda like the old lemmy system (as on lemmy.world), and nothing gets deleted except the user page (which also seems to get federated), the posts and comments stay up.
Thought this would be interesting to some, if i had known what a mess this would be (obviously expected some federation issues, just not like that), i would have manually deleted everything. I deleted all these accounts in December, maybe this has been addressed somehow in the meantime, personally i'd have trust issues in this process.
I get that world should be an outlier. World does not have the checkbox, it just says "esto eliminará permanentamente todos sus datos de esta instancia" :) Thought that would include posts etc, but if i understood that right, it was working as intended.
As for the other instances, i did use the checkbox and the accounts etc are gone from the home instance but not anywhere else - at least that is true for the slrpnk account on all the instances that i checked.
Now i'm surprised to find my lemm.ee account is actually gone from lemmy.ml and db0. But it is not from world, slrpnk.net, lemmy.ca, sopuli, blahaj, feddit.org, jlai.lu, discuss.online, infosec.pub, programming.dev, lemmy.nz, but at least something seems to have been federated with this deletion.
I deleted those accounts in late December.
I deleted a newly created account on jlaiu.lu two days ago, they're running 0.19.5 but i think they have the checkbox (which i have then ticked) and my comment and profile deletion has federated nicely over the instances that i checked.
I would not know how to reproduce all this. I just deleted my accounts and checked the checkbox if it was available.