If you report someone as unskilled under level 30 they are forced to play a couple of bot games before they can do normals again. If you report a level 30 as unskilled.. Nothing happens you don't lose ELO or get replaced in the matchmaking system at a lower skill cap you really just have nothing happen to you at all. I was told this by a friend who knows a ton of people who work at Riot. Matchmaking is already all kinds of crazy =P