I think it depends on two things ... Trust and intent.
For example, my anxiety and depression at times cause a large amount of strain on Indigo and our relationship. If he has a partner who can help with this, then that is a good thing.
That said, it's all in how Indigo presents the issue. If he vents to a third party about me with no intention of seeking advice, that could be hurtful. I say could, because he has every right to vent. But would I feel good about him venting to anyone he hasn't known very long, regardless of whether they're a friend or a love interest? Absolutely not. It would be a betrayal to me. If he needed to vent to someone he has been close to for longer, or someone I trust, well that is entirely different.
If talking is for constructive purposes, then I give him free reign. I trust him not to paint me in an evil light, and really do welcome input that could potentially help our relationship!
Our loves should be our friends. I think it's important for everyone to realize that sometimes we all need to lean on a friend for support, potentially in areas that might not be any of their "business". I trust Indigo to lean on the right people.