So what do i do about server hackers using multiple accounts? in a public lobby?

I'd suggest getting into IRC and get a GM to join your room and otherwise screenshotting is always a good idea.

Just for the record, it isn't hacking.

The term you are looking for is Multiclienting, which is the act of opening multiple Toribash windows and joining the same server. People who do this will usually have "MC" next to their name.

For example - Cheshyre(MC)

And yeah, doing this in official servers is against the rules. So if you see it please hop on #support to get a staff member or make a report about it.