Muting a player does silence their emotes. If there are some it doesn't, report it as a bug.

https://www.youtube.com/watch?v=Nk9HM7qCYrM

They included silencing emotes into the Mute function a long time ago. I just recorded this to demonstrate it. There seem to be some noises that aren't silenced, so if you are trying to mute them and it doesn't work then record it and submit it as a bug so they fix it.