According to the dev and some people, the frontend is more performant than Lemmy/Kbin/Mbin due to the smaller data sizes. I read that it was because the dev came from some african (?) city where they only had like what, 2G internet connections?
As for the disadvantages, I can't say I find it great that it is written in Python. I don't like interpreted languages in production. That's all. Comparing the performance of it and the backend of Lemmy wouldn't be fair, since Lemmy's backend is written in Rust (compiled).
Yes. Though not all features are federated (yet), for example flairs.
Unless platforms start implementing the DID standard, this will be hacky to accomplish without weird artifacts. One other way is to do it how Mastodon does it, but that does not bring your content with it.
It seems like nutomic is in favor of this idea. He stated that he wanted to implement such a thing in the future when most bug fixing is done. So we definitely could see this during the v1.x.x releases: https://github.com/LemmyNet/lemmy/pull/3303#issuecomment-1607459130
Do the communities appear in your subscribed feed? If yes, it's most likely an UI bug.
I am not sure why you'd ever expect other instances to delete your content when you delete your database. Every instance saves a copy of your data; the content isn't being pulled from your database. And deletions in the Fediverse are mostly useless, as you can be sure that there is some instance out there that ignores delete requests or doesn't understand them.
Neovim.