I agree that things can be misinterpreted, but that's not a reason to avoid relationships with people. It's a reason to keep things clearly communicated. And if people choose to gossip and act like high schoolers, let them. Maybe call them out on it, depending on the nature of your professional/personal relationship this can be easier said than done.

But, maybe this is just me, I'm not going to forfeit my good relationships with women (several single, attractive) just because my SO is getting jealous. If she doesn't trust me, then that needs to be addressed directly. And if she can't trust me, that's a bad sign for the relationship in the long-term.

If my coworkers start rumormongering because I go to lunch or coffee with a female colleague, they need to grow up. Men and women are quite capable of having professional, and personal, relationships that remain entirely platonic. And barring these sorts of professional relationships on the basis of gender means reducing the professional network of both people, which can result in long-term career setbacks. This is exactly the sort of thing that can hold women back in a male dominated field.

I'm going to side with GP's motivation. While it would be great if people didn't rumor-monger when they see two coworkers spending time alone, wishing it were different doesn't make it so.

There's a lot at stake. A simple your word against theirs or miscommunication can land you in serious HR trouble. This issue is incredibly sensitive and very charged. Why risk it?

Two reasons. First, these relationships are important to me in various ways. Second, because not acting means leaving or even encouraging the status quo. I'm willing to risk it because I trust the women that I have these platonic relationships with to not levy false accusations. So long as my judgment is accurate there's no material risk to me. And when it's not, I'll deal with it.

Are you single? You sound single.

I'm not single. I'm a woman, even. And I have the exact same theory as he does. I expect to be able to be friends with whomever the hell I like, and my husband has the same. I don't have to spend time around his friends if I don't want to, and the same for him.

I have a good enough relationship that we can both express distrust for the friend, but that isn't something binding or obligatory to follow. If I find myself jealous, that is a problem I need to overcome and not take out on him and I expect him to do the same. I don't have reasons not to trust him, and if one doesn't trust their spouse, perhaps they should address that issue.

I'd not enter into a long-term relationship thinking this wasn't the case, honestly.

No.