What would appropriate HR policies be? The following is what I thought of, and rejected (note - I'm not a lawyer, I don't know any laws about HR, and most importantly: this is all highly hypothetical, I haven't even considered starting a company yet):
(1) forbid "workplace romance" - this is very against my philosophy of encouraging personal freedom, and I don't think I would want to work for a company that had this policy. Moreover, I don't think this would solve the problem - false allegations could still be made, and true allegations could still be denied.
(2) disciplining the one who makes the inappropriate action - this too has the "he said, she said" problem as above, and furthermore the appropriateness of the action is often determined not by the subject's action itself, but how the object perceives it.
The best policy that I can think of is: all employees are expected to act professionally in the workplace, and to not be affected by their emotions (if they can't manage that, they should take a day off). Workplace romances are discouraged, because they may result in hard feelings between employees, but if you think being with the person is worth risking your job, go for it. In case two people have a conflict unrelated to their work, they should handle it as adults. If they expect action from the employer, they should present concrete evidence (emails, code commits, phone call logs, voice recording of the conflict, ...).
I realise that this sounds a bit harsh and insensitive, but that's what would work for someone like me - in the rare instances where I disliked my coworkers, I put my feelings aside and consciously decided to give them "another chance" by recognising all the great work they do. What are your thoughts, and what kind of policy would you suggest/instantiate?