If you repeat a problematic behavior such as AFKing you may get a sanction.
If it's an emergency from time to time, nothing will happen.

Remember it's a team game, most people queue in dungeon expecting a maximum of 20 minutes in and out.
While the flaming is not acceptable, griefing by afk/not moving is not acceptable either.

Never forget you are playing with real people that may not have your time.
There are players who come back from stressfull work and simply wants a simple good time, as much as you.