(On LiquidThreads/Redesign#Summary_Issues.) It would be useful to have a different control to actually declare "closed" a discussion and make it appear as such, to avoid current crappy solutions like w:en:Template:Closed, m:Template:Status or worse.
Topic on Talk:LiquidThreads 3.0/Design
I absolutely agree with this. The reason this isn't part of the design as it sits is because we decided that it would be a feature that could be "shaved off". The communities already have solutions in place that can work for the time being until the best solution can be achieved.
There's another issue, too, which is a question as to whether or not old, expired, or closed discussions should be reopened. Having a "closed" flag for a discussion would create an assumption that replies cannot be added (which may be desirable).
But to my mind, one of the reasons that discussions get "closed" is because they get rolled off into an archive, never to be seen again, and people get tired of the same topics being brought up over and over again. LQ solves for this: the archives are there, and you can search for existing topics within them.
Either way, the feature (which I like) requires some heavy thinking.
Another reason to mark a discussion as closed is that in this manner users know they don't need to read that discussion, while their input is needed in other discussions. Sometimes there's a long talk page with some ongoing discussions and you won't archive a recent one, even if it's closed, because an older one requires some more comments, even if it's not active (and archives are usually chronological). With current LQT you could bump all non-closed discussions to move them on top, but I don't think that this would be an appreciated system.
I've also filed a bug for this: bugzilla:24815 (see also bugzilla:24814 whuch is [almost] a proper bug).