> On a semi-related note I sometimes miss the
> ability to mark a set of non-contiguous threads / messages for action
> (like 'm' in dired). 

That would probably the most general way to go. Then one could also
build the equivalent of dired's '% m' and '% g' to mark based on some
sort of query. However, it would require reconsidering all existing
commands in the context of marks, wouldn't it? For example, what would
happen if I pressed 'RET' in the search view while multiple threads are
marked?