I feel like I remember reading or even actually writing something about this some time ago. But I wanted to bring it up again because to me personally it seems like a bug. I'm running the latest devel-threads branch, and if a thread is collapsed and I drag it to another folder only the top-level message is moved, the remaining messages of the thread don't get moved. This seems unintuitive to me. In my mind it makes more sense to move the entire part of the collapsed thread from the point that thread was grabbed down. Some months ago I had implemented this in my own testing install. I can't recall now if it worked 100%, but I think it mostly worked:
http://code.nkinka.de/gitweb?p=roundcube.git;a=commitdiff;h=f3bb47d0e30a2e58...
There is a side of me that feels like if any message in a thread is grabbed and dragged to another folder that the whole thread should probably be moved to, but I can see how some people might find that shocking and disagreeable. Really, the path forward should be the Gmail approach of one giant bucket and using tags. The folder paradigm is sort of broken by nature, but that's another story.
Nathan _______________________________________________ List info: http://lists.roundcube.net/dev/