does reporting actually do sth?

i just had another endless wont quit game. four lakes first up just sits behind walls and waits with bbc. and after i kill him he hides with ships and elite canon galleons and stalls the game out. tbf he was so bad i should have killed him earlier but oh my god this is annoying

so when you report for griefing will this person be warned or punished or wont they do anything??