I just played competitive and ran accross a group of players named "gauchos", who essentially ALWAYS will vote in favor of their friends, no matter what (as long as its not blatant game throwing).
No attempt whatsoever to scum hunt will be made. They will always lynch unknown over their friends unless the unknown is clear.
I believe this gives them an unfair advantage, and makes the game a bit boring, but i didn't report them because i didn't find a rule that they broke.