misericordiae

Definitely sounds like Mirrormask to me.

This looks great!

[…] There are also instances with varying levels of moderation, which may be encompassed in this.

I know you didn’t really touch on what the moderation aspect might involve (and maybe you have provisions for this in a section I skimmed), but ideally I would want defederation lists to be included somehow, at least as an advanced option. Does the user want/not want an instance federated with [other instance]? And then, before final instance selection, present the full list just for verification.

It’s on youtube in full (with subs, legitly, from Tencent) if you want to keep watching it: https://www.youtube.com/playlist?list=PLMX26aiIvX5rFSYPXtcqda3tWd6pGVD5Q