I’ve always thought of the StackExchange network as kind of a strange beast. In one sense, it is basically a Reddit clone. It has a “front page”, it has “karma”, it has “subreddits”, etc. And yet, it is something else entirely. Through strict moderation and constraining site rules, it has always maintained a separate niche from Reddit, despite being so conceptually similar.
I think there is a real possibility that StackExchange network is basically already compliant with the “threadiverse” protocol (ie the Lemmy/Kbin dialect of activitypub), or rather that the data model of their API could be made to be compliant with almost no effort at all. I think it would be really cool to see some of the questions and discussion threads that get created over there appearing over here. Even if it was a one-way connection, the idea of knitting these networks together is fascinating to me. I have no idea if it would make business sense for them, but then again I don’t actually know how StackExchange makes most of their money.
There are ides to make similar q&a platforms part of fediverse.
I doubt SE would join fediverse, and I doubt we would accept them. I personally would like to have similar opensource platform part of fediverse, but not them. Most of us don’t like how it has been run and looks like they are on their way down, similar to reddit.