Wow. That is some heavy-handed, misguided "justice" there. Banning people's Google (including GMail) accounts, even rejecting appeals, only for using emotes the way it was requested and encouraged by the streamer they were commenting on.
The thing that was apparently against unspoken Youtube policy here was this kind of interactive, emote-driven streaming. But I get the impression Markiplier didn't get banned, only their fans.