[riffraff]

hearthstone also allows "Thanks", and it is also used when you make a mistake (although there is also a "mistake" text).

The interesting thing is that you could actually say "thanks" (or "well played" or "hello") in a neutral way, but if you are on the losing side you are very likely to interpret them as mocking any way, which personally increases my annoyance at losing wildly. I desperately crave for a "f* you" emote at times.

But blizzard has been smart: you can preventively mute your opponent, and just get rid of the thing altogether.

[smcnally]

Mute sounds great. It also aligns interests: if you want to be heard, you won't want to act like too big a jerk. Be interesting to see how the mutes are manifested: is it quiet -- you know you've muted me but I don't -- or more-widely communicated? Be great if the mute action was broadcast to appropriate players. "riffraff has muted smcnally." Then others would have less tolerance for my nonsense if they had affinity for you, or they might view you as overly-sensitive if otherwise. The latter would govern abusive or reasonless muting.

[riffraff]

AFAIK there is no indication that you have been muted, which I think is in fact not ideal, as I agree with what you say: you should know when people find you annoying (thought that might encourage the behaviour for trolls, not sure)