First of all, moderators, while I disagree with this guy's opinion, it's not a troll. It's just an opinion we disagree with. Learn the difference.
That said, making a sexual advance to a subordinate right off the bat is just plain stupid. You don't know each other, and anyone in her position would feel uncomfortable. It's an office, not a bar. People are there to work, and what's more they can't avoid each other. That's why you need professionalism in your job conduct.
HR's response was also stupid. In business you often get into trouble by saying too much, and that's exactly what they did. They could have said, "We've issued a verbal and written reprimand and will be watching this situation closely; let us know if more this kind of thing happens." Instead they had to bring in the fact that this guy was a "high performer", implying at least that this gives him a license ordinary managers don't have. Now I think we can all assume that on some level high performers get leeway that low performers don't. But saying so is stupid. It's pretty much tantamount to a confession that you don't take this seriously.
Then they compound the stupidity by telling her to expect a bad review from this guy because she brought this up. This pretty much is an admission that HR and management countenance unprofessionalism, allowing managers to use employee reviews to pursue personal issues rather than evaluating the employee's contribution to the company.
That's just asinine. If it's false you're undermining employee confidence in the review and performance reward system for no reason. If it's true you should be fixing it, an in the interim keeping your mouth shut.
Now I'd say you should keep your work and personal (e.g. sex) life separate, but I know some companies don't give employees time to have a personal life. If a company does that you're absolutely right, your HR people are going to have a tough time navigating the line between advances and harassment. All the more reason not to be sloppy. If someone in such an environment can't broach the subject with tact, he'd better be prepared to be celibate.