Did you stop recording to try to avoid arguments about it, or because you agreed with her that it was wrong and a violation of her privacy?
BeagleGirl, great question - and the answer is complicated.
There was always a seed of doubt as to whether I was being "ethical" - she had no idea, it seemed like maybe it was wrong, but I felt SO desperate for SOME validation that I wasn't the crazy one, I did it any way. I had the same philosophy as formfiler - I used the recordings twice, both times inside a therapy session, and both with the honest goal of improving the relationship.
When pwBPD found out, you can imagine there was a VERY strong "victim" reaction. I just had a conversation with her an hour ago, where she told me that I had done "like, Amnesty International level bad stuff" to her. She has said multiple times I've violated her human rights. So with that kind of attack, I couldn't help but let my own feelings of guilt get a little more air time in my head.
But like I said, I'd go back to doing it again in a heartbeat if I could be 100% assured it would never get detected.
So I guess the answer is: I'm avoiding arguments. ;-)