As described in the bug report on kde, kopete does not deliver outgoing messages because a bug in the stealth feature. The patch supplied fixes it. Tested on my system. Patch and ebuild attached. Reproducible: Always
Created attachment 226533 [details] Revbump kopete ebuild that applies the patch
Created attachment 226535 [details, diff] Patch that fixes the stealth feature
I was having the same problems, this fix works for me.
Fixed on kopete-4.4.2-r1. Thanks for looking into this and providing the link to upstream bug with patch. I don't use yahoo, so I'd appreciate if anyone using it could confirm the ebuild fixes the issue.