I just do-not-pass the / key, or enter. Also the movement keys.

So, I can chat on my main using /w or /r, or just enter, but then the spacebar makes my alts jump a lot and if i happen to use a number in the chat then it triggers them to try casting a spell or whatnot. Not a big deal as all my cooldowns are on keys I wouldn't hit in chat.

If I want to have a real conversation I just hit the pause key before chatting which triggers the mute, not a big deal and only takes a split second to turn off and on.