Hmm so the Feed actor mainly consists of a following collection and uses Add/Remove activities. This really sounds like it should be a Collection and not an actor.
Opt-out on the other hand for public feeds specifically is something that I support. But then good luck having that supported on lemmy where almost all communities exist.
Lemmy already has a setting community.hidden so that communities dont show up on the All feed. But this is not easy to access at the moment. I can fix that.
Originally account deletion would always delete your posts, comments and everything. This was changed in 0.19 to make the content deletion optional (otherwise a lot of posts and comments would disappear unnecessarily). Unfortunately we forgot to add the new option to the user interface for 0.19, but it was added probably around 0.19.4.
Its hard to say why the federation didnt work properly, maybe there was a network error, or a bug in older Lemmy versions that got fixed in the meantime. Or there is still a bug which only happens in some cases.
When deleting the account did you mark the checkbox "Delete all posts, comments and uploaded images"? Lemmy.world is running an old version so its possible that this is missing. Without that it is expected that only the profile gets deleted, while content is still available.
As for federated account deletion this is implemented and covered by test cases and should work in theory. However it is always possible that there is a bug. It would be helpful if you could open an issue with exact steps to reproduce. Use enterprise.lemmy.ml and ds9.lemmy.ml to test the latest version.
That would take a significant amount of work to implement, and we dont have the resources for it. But all the code is open source, so youre welcome to give it a try yourself.
We haven't banned anyone for trying to contribute. If you're talking about bans from lemmy.ml, that doesn't prevent anyone from contributing on Github. Besides, the whole purpose of Lemmy is that there can be different instances with different moderation policies.
I dont think its a good idea to give money to Google or Bing for advertising. It would make Lemmy appear like a commercial project and give false expectations. And we barely have enough money for development so in my opinion money its better to donate. However if you have money and want to spend it on advertising, nothing is stopping you from doing that.
Are you logged in on those instances? Resolving a community name like that requires a network request, if you are not logged in it doesnt work.