You aren’t clocking the situation correctly.

I’m not responding to the situation at large, I’m responding to your comment in isolation.

someone who trashes their partner (implying habituality), isn’t someone to trust with sensitive information

I don’t believe I agree with this, with the qualifier that I also don’t agree with trash talking your partner to begin with. I don’t think you’re right that if someone talks negatively about their partner that they can’t be trusted with information. Maybe it’s a cultural thing.

Also note that I said “trash-talking” where you said “venting.”

I’ll use trash talking from now on if it helps.