A. Is this threat serious (can it be carried out)
If not don't worry about it
B. Not unless you have admin and they have it set up to log the IP on posts AND they aren't using a proxy or something. Though you could also sniff the traffic i guess but that will just tell you who connects not who did what.
C. You would then have to either: A. Dox the person/'s, B. Hack them (not recommended)
If you Dox them then you would have to send them that info and basically counter threat.
Sorry to hear this, pretty stupid question to be honest and not sure i believe you but whatever im just procrastinating from doing homework xD