Sometimes your friend might be making a bunch of noise - maybe there's a crying baby, or they're asleep and snoring, or maybe there's just too many conversations going on. You could mute them to help you hear... but it's easy to forget to unmute them later, particularly if you have nameplates off. Having an option to mute a player _without saving the mute serverside_ - that is, taking effect only until either you or the mutee changes instances - would be helpful for these situations.