Sound effects from one direction don't necessarily affect both speakers in stereo
If an NPC to your side is talking, you will hear zero audio of the NPC talking from the speaker on the opposite side your head.
If you're using earphones, but only one of them is in your ears, you won't hear the NPC talking from the other side of your character. This is problematic, as that ear should at least be able to hear the NPC at some level, even if it is reduced compared to the other ear.
This problem isn't limited to NPCs talking, but also to non-music sound effects.
(RM-776 from redmine: created on 2013-05-11 by Paul McElroy, , closed on 2015-12-27 by Chris Robinson)