We've had a first taste of utilizing the conversations api in applications now. Pleroma FE has a MR for it and Kenoma is almost in the same boat. There's some UX worries that have to be sorted out that aren't just frontend or backend problems I think.
Conversations timeline: It gets very confusing when there's more than 1 'conversations' with the same person, most chat applications don't allow this sort of behavior and instead all messages with a single person are in one continuous timeline. Should we just deal with it or figure out a solution?
Participants being dropped or added during conversation: tagging users makes no sense in chat context, addressing should be done purely by members list in the current conversation. There might be some other solutions for this as well but we can't do the conversations list in a sensible way if the addressing can change per message.
Public threads turning into dms: this is the big one, you can end up with completely nonsensical "conversations" where most of the messages were never addressed to you, but it's still your conversations because someone sent a dm reply to you in that thread. I think in these cases the conversation should only return the dms that have been addressed to you and nothing else. Some context could be added on top saying that "this conversation started as a reply to some public post" or something.
Without addressing these problems I think the conversations is a worse experience in pretty much every single way compared to current DMs. I do want to see this feature done well so that pleroma and fediverse in general can closer to competing as a good free chat platform.