On the eve of me working on federating out mentions from NodeBB, I've started thinking again about how they're used in the fediverse via Mastodon. I've gone on at length about this before, but it bears repeating again:
I think it's absolutely bonkers that replies dogpile mentions just so participants stay in the loop.
It has the unfortunate side-effect of looping people in to a conversation merely because they were mentioned. The even worse side-effect is that if you don't follow along with this convention, the people who are left out simply aren't notified and drop from the conversation. Awful UX!
Mastodon does it because other than a follow, like, or a boost, a mention is the only other way to land a Note into your notifications. So you'll see exchanges where multiple users all start (or end) their posts with a string of mentions as they're having an ad-hoc group conversation.
> @foobarbaz @barbaz @quux did you hear about the latest news out of...
This doesn't happen in forums, mostly because if you interact with a topic, the baseline expectation is that you're subscribed to that topic in the future. Replies get sent to your notification box or other dedicated UI widget, and you can easily keep track of your long-running conversations.
In NodeBB, a response within a topic causes the user to automatically follow the topic. Future actions in that topic notify all followers. We collapse related notifications to limit noise, though that is an oft-cited concern against throwing things in a notification inbox.
It sounds like I'm hating on Mastodon, and it's easy for me to do because they're the big fish in the fedi sea, but I still feel this isn't something that needs to exist. Mastodon could potentially create their own dedicated list for "conversations you've interacted with".
I will admit, though, that it is a lot easier to present that data when reply chains are grouped into topics :)