I’m not being funny but you know that your HR colleagues aren’t the organisational police, don’t you?
I’ve worked in HR for a looong time and HR are there to support and guide the process… they may help with decision-making but 99.9% of the time they are supporting operational managers to make decisions.
If you’re not happy with the outcome, they should have offered you the right of appeal. You can still ask for that.
I get what you mean about the sexualised nature of the comment but you probably really needed to provide a lot more information about the context, tone, and why you think that he thought it was ok to do this. You should also have explained the outcome that you wanted.
If your own manager or another senior manager above you is allowing or enabling this behaviour generally, and is not open to assessing it, then that’s your actual problem.
Also really consider carefully people who say ‘you could go to ACAS and get a settlement’. In many cases you have to be so incredibly distressed at what has happened to resign with immediate effect. So don’t take that path lightly or think it’s an option unless (sadly) something pretty abhorrent happens to you.
FWIW I think the comment is probably marginal. But you should be able to speak out about a culture at work that is fundamentally sexist or inappropriately sexualised.
In your shoes I’d be looking for another job… the culture is very unlikely to change there without significant changes to senior leadership, and I just wouldn’t want to work in that sort of environment.