news.gmane.org is broken, so sorry for breaking the threading. I read about the POP3/disconnected IMAP filtering problems.
What I can say I extensively use both and have filters for both. The few things I noticed so far are: - after resume from hibernation, the filter agent can be busy (not sure why) for a few minutes - after resume from hibernation if some mail arrived meantime to the POP3 inbox, they might not be filtered - ocassionally (but not more than 1/day), I get a conflict dialog
What I didn't try yet is spam filtering on online IMAP.
In any case, there will be a KDEPIM development sprint next weekend. Test the latest version (if from source, even better, if not, try the latest release), gather as much information/logs as possible, find how problems can be reproduced and report them as bugs, so I can look at them at the sprint.