If the examples above don't scare you, then by all means, leave things as they are. If you want to prevent a problem, however, then establish the fairest policy that you can. Well, start with being discreet. Or perhaps, just perhaps, the company will accept the relationship if you are open about it, have a strict working relationship while on the job, and do not have a reporting relationship. Perhaps what fertilizes the grapevine fastest is the attempt to hide a relationship which, if open, might be accepted.
Most grapevines have root rot, but it seems to be the biggest weed that thrives on garbage.
If you are forced to leave, it might be considered unfair, but it is just another condition of employment that you agree to when you join a company. You can rail about the unfairness of it all, but that's the nature of the workplace today.