What grinds your DOTA gears?

What grinds your gears, things other players do is especially applicable.

Mine is the backseat drivers, I play in Europe I find this is much more common in Eastern European servers, which btw are the most toxic servers I've ever played on.

immediately checking what everyone has bought, pinging every 5 seconds what they want you to do, stopping to type "When you press this Q, you should then press the W."

"I DIE N U HAVE GRAVE ******** "
"that was 5 minutes ago…"
"ROT IN HELL U ******* "

If your first reaction in a game is to check what everyone else is doing – you're the problem for the bad MMR, not everyone else.

Edit: the grave was an example, I've only played Dazzle twice. Relax boys. No one actually yelled at me for that.