I will say that, as someone with more experience on Fedi than Nostr, that it isn't uncommon at all to run into reply threads where you can't see half of the participants because of your instance's defed list, so us being able to see these users at all is a step up in that regard, but I do agree that some kind of visual indicator to differentiate ActivityPub users that can interact with us from ones who can't would be a really good idea.
Discussion
So let me get this straight... Is it the case that IF an instance federates with Mostr, then we SHOULD expect the bridge to be 2-way?
Or are there other aspects of the interaction (user preferences etc) that dictate this?
I believe other aspects are at play, but my understanding is that if the Fedi instance is federating with Mostr, the interactions should be 2-way, yes.
I think there are some technicalities in how federation works / populates that may make connectivity <100% reliable, but these are nuances that Alex would know better than me. I'm basically just here to give a tech-illiterate end user perspective lol