A simple-ish solution is for a mod to PM the offender and ask for an explanation, and figure out a corrective (if necessary) and retributive (if necessary and appropriate for deterrent) solution. Then implement it, make a public note, and be done with it. Very imperfect, mostly due to personal impatience with forum meta, but mostly gets the job done.
Below is a message I just got from jackk. Some specifics have been redacted 1) so that we can discuss general policy rather than the details of this specific case 2) because presumption of innocence, just in case there happens to be an innocuous explanation to this.
So... thoughts? I have mod powers, but when I was granted them I was basically just told to use them to fight spam; there was never any discussion of any other policy, and I don't feel like I have the authority to decide on the suitable course of action without consulting the rest of the community.