Lol, that looks like an electric one more like the robot ones.
He's holding it down with a stick because it's moving way too much.
It's actually a metaphoric gavel held by an anonymous ordinary citizen who has been empowered to be the judge over the rest of society, depicted as a mindless Roomba.
This is especially significant in an online forum, where faceless people have the power to pass judgements over others.
How's that?