The subject itself is pretty self-explanatory.
There should be a feature that allows users to report other users to the admin / moderation team.
Some limits might be necessary, for example, accounts younger than 1 week can’t report or can’t report more than 1 username for 24 hours, to avoid possible abuse.
You can report the user by opening a support ticket.
I was unaware of this.
Under which category should this go to though, none seem to fit.
Report advertisement (I was the poster, not the user)
Ah, sorry about that confusion. We’ve just added a separate “report user” category.