I'd like to add a few thoughts to this discussion, if I may.
I agree with Floris: the way XenForo currently handles people leaving a conversation can be inappropriate for a business environment. I can think of a variety of ways that it could cause trouble for users.
Ati is correct in saying that it's unlikely users will leave a conversation by accident (so long as we ignore those who blithely say okay to confirmation dialogs without reading them). But this overlooks an important issue, which is that XenForo does not specifically alert the user to the fact that
the other participants will not know they've left.
If a user assumes that a conversation is done and chooses the second option to leave it (not realizing he should keep open the possibility that it will continue), all the remaining participants are left in the lurch. They may spend a lot of time crafting a careful message for the person who's left, and become a bit peeved when they later learn that they were talking to a blank wall. (And it doesn't stop there: XenForo won't let them re-invite that person, so to complete the communication they'll have to cut and paste what they said into a new conversation.)
I don't think it's only admins who will find this behavior irksome. Inadvertently broken conversations between users could also cause unnecessary friction between forum users, which admins would be well advised to avoid.
In this respect I think XenForo is being a little too elegant for its own good. Users should not be allowed to accidentally treat each other as if they're being abusive. At the very least, XenForo should make it clear to users that (a) they are choosing an option that is intended for use in specific circumstances, and (b) this option will result in the other users perceiving them as still participating in a conversation which they are in fact ignoring.
If XenForo does not make this clear, that puts the burden of explaining this feature on the admin's shoulders. Which means we have to post an explanation somewhere in the forums and hope everyone reads it. (I'm sure we all know the chances of that happening!
)
I also think that XenForo could do a better job of indicating to all participants when a user leaves a conversation without intending to ignore it. At present conversations just seem to go on indefinitely; users may want a way to signal that they think the conversation has accomplished all it was meant to, so everyone can let it drop. Actually telling people that the user has left the conversation and decrementing the participant count would certainly be a start. Treasurer had some more good ideas for this, and I've incorporated them into a suggestion I posted
in this topic here.
At the very very least, though, XenForo needs to do more to alert users to the consequences of their choices.