Terri Oda writes:
Is it possible to split or merge threads?
Posters can split off a thread at any time by just replying to +new instead of the existing thread.
So if somebody is subscribed to the old thread, and their default is not to automatically subscribe to new threads, they lose track of the new thread?
There is currently no way to merge threads.
OK. That's hard to do (and keep users happy).
I can't think of a better way to handle [threads that migrate from one list to another] off the top of my head for much the same reasons that correctly threading archives is hard.
As long as you don't try to support merging threads, and people provide accurate reference or in-reply-to headers, archive threading is pretty much a solved problem AFAIK, as long as you have access to *all* the lists. What's hard to do at the server end is provide killfiles. That's also a solved problem on the client end, but for some reason people want the server to do it for them.