If you are truly sitting to be paid in the right seat as a passenger (safety pilot) for an aircraft that is single pilot and the certificate holder is issued A015 for Autopilot in lieu of SIC your company is correct and they are not in violation of any regulation by doing so INMHO. Many brokers/ passengers will not charter aircraft with one pilot on board for the fear that if that pilot becomes incapacitated what are they to do. Because of this many companies put a contract pilot in the right seat to make the customer comfortable/happy.

That being said this is where most of those companies are in violation...

Are they actually marketing the trip as a qualified 2 man crew? In addition the moment the guy in the right seat keys a mike, reads a checklist for the PF, pushes a button, listens to an ATIS on the behalf of the pilot the company, PIC and Right Seater are in violation of 135.95 and 135.115.

You are correct this is a very grey area because most will do the above. Will the right seater really sit there purely to keep the pilot awake with good conversation or are they expected to do something. However if you sit in the right seat and do nothing other than sit there on an aircraft with no more than 8 passenger seats not including a crewmember seat show me which FAA regulation you are violating.