If you exit Kaffeine while its in 'pause' mode, a couple of seconds of the paused title will be played while Kaffeine quits. Reproducible: Always Steps to Reproduce: 1. Play a playlist in Kaffeine. 2. Pause after a while. 3. Quit the program completely (not just close the kaffeine window). Actual Results: Some of the paused file is played. Expected Results: Kaffeine should quit quietly.
This does not seem to be Gentoo specific, you should try with the latest kaffeine version and report a bug to kaffeine authors in case it persists.