Play at your own risk

trekbike

I'm sure I will add others as time goes on but this first definitely needs to be on this list.

People under estimate the risk.

http://www.independent.co.uk/news/world/europe/man-stabbed-to-death-over-game-of-chess-in-ireland-9054595.html

You did this already (warning against Players). I think the way would be to send Feedback. Publishing their names could be harrasment.