

Sorry but what exactly do you communicate and access between discord servers? Are you talking about PMs which are by default independent of servers?
Unified search could easily be achieved through third party tools at the least, like for IRC. I don’t think even discord has unified search between servers.
That’s true about DM, however DMs are not a core use-case for discord-like services. It’s the group/voice chats etc. I could see a workaround like lemmy does, where if you want to DM a user in another server, you might be able to do it through your fediverse instance (i.e. a DM simply has your fediverse instance DM their fediverse instance), but I’m sure there can be more elegant things like. However DMs by themselves are a weird thing by themselves, so much so, that even bluesky had to bolt DMs on-top and outside of their protocol.