I have read many threads on here about telling the AP's spouse/significant other about the affair. The main reasons given in favor of this seem to be 1) they deserve to know, wouldn't you like to know if you were them(and, you are them). And 2) to make certain the affair is exposed - affairs thrive in secrecy.
I do agree with these reasons. In addition, I feel like exposing the affair is an important act of self-care and self-love. What I mean by this is - our WS's chose to cheat, lie, deceive along with their AP's. It was not our choice or decision. I feel that in most cases, not telling the OBS what we know also taints us with some of WS's moral poison. Makes us an indirect party to the betrayal, even a facilitator. Who needs that guilt or bad feeling, on top of what our WS's have already dished out?
I know everyone has a different situation, and must make their own choice based on individual circumstance. I chose to tell, and I am so thankful that my conscience is clear. It's a small bright spot, that I did not lose my integrity because of what HE did.