My advice is to always, and I mean always, be polite, courteous, and informative. Instead of raging and freaking out when someone says 'what's mia', how about you explain it? Then a) they know what it means, and b) they're more likely to do it in future. By taking 10 seconds out of your game, you've given 4 people some information that will make the game better for everyone they play with. Ever.
If everyone just acted like the mythical gamer they always complain isn't in their games, the community would be that much better.
p.s.: Nothing pisses off a troll so much as someone who is polite to them. It's like soap or sunlight to them.
"u mad bro?"
"I'd say I'm mildly agitated, but this is a game, so I'll keep my atttitude positive."
"y u so mad bro?"
"If you misconstrue my previous response as an indication of upset, you must have difficulty distinguishing emotion in your personal relationships."
" /sad trollface"