But that is always going to be a problem. Wouldn't this fall under the description of a "Nazi bar" phenomena? Like, you and I may not personally be Nazis, yet Lemmy contains propaganda (tbf, more for Alt-Left tankie shit than Alt-Right Nazis) and if someone were to peer over our shoulders and see such on our devices, they could (strongly?) question how much they want to be friends. Literally 100% of the people that I've recommended Lemmy to irl have actually chided me for having suggested it. It's baked right into the name of "Lemmy". It doesn't help one bit either that the top Google result for that term is lemmy.ml, which shows Local rather than All by default.

While we may carve out and designate a corner of the bar to be "ours", so long as we are still inside the Nazi bar, can we really be so surprised at who else comes in here? They write the code, and ultimately it's more theirs than ours, so e.g. if they want to allow Hexbear alts on their instances, then what can we really do about it?

Btw two other features that PieFed offers that are relevant here (it really is quite superb when it comes to this stuff!) are the ability to block a "Domain" and various keyword filters. The former is a feature shared also with Mbin but is so heavily buried that I've seen feature requests that went unanswered for it, but if you know how to make it happen then Mbin can do it as well. And some apps - possibly Sync and/or Connect but I dunno. Though PieFed definitely can block not only the users from an instance but also links to it as well. And not just Lemmy instances, but anything, like if you wanted to block all URLs to the Washington Post or New York Times or some such, you can, easily (Account -> Edit Profile -> Blocks -> Domain). Lemmy is the Alt-Left Reddit, so I doubt you'll ever be offered that feature where you are at, except again from (maybe paid?) apps.

Here's an example post that shows an image that is hosted on lemmy.ml, which lemmy.cafe has blocked, but shows up anyway. Also, I note that defederation leaves intact all the older posts - e.g. here is an older community whose content remains behind after defederation (even though newer content does not come in).

Anyway, if someone wants more features, then it will need to be built. As PieFed, Mbin, etc. are doing already:-).