Some thing similar happened to us in SF in 2010 (throw flames all you want, ABB was new, we didnt realize we were breaking rules, we thought we were just making money while out of town, as that was ABB initial marketing ploy) The property managment company booked my then apartment atleast three times over the course of 6 months. To prove I was violating my lease, etc. They ended up paying thousands in reservations to do this, and bc of SF rent laws all I had to do was stop when they asked, to be able to stay in my apartment. It was a very interesting situation to say the least.
Im not sure the legalities of this bc a few weeks after the last 'planted' person stayed I got a call from their lawyer asking me to sign a release not to sue in lieu of a nice payout. I would reach out to a lawyer and ask them if your HOA can do this, I would think it falls under harrassment.