Or, and this is what I did when I saw it on the forums. /who smp1 /who smp2 etc until you see a green name/purple name and PM them in game, but only do this in emergencies like that one.
You have to wait 30 mins to report the same person again, not to report anyone. For example, say IcecreamCow and JustinGuy were swearing in chat. I could do /report IcecreamCow swearing and /report JustinGuy swearing in the same minute, however if I wanted to report ICC or Justin again, I'd have to wait 30 mins. However, if Shaunwhite1982 then started swearing a few mins later, I could still report him since I've not reported him in the last half an hour.