To those that are okay with dating a separated person, how would you feel about a person that dated your spouse while the two of you were separated (either physically, or in home)?
I don't see how the 'separated' status plays into this. It definitely $ucks to see someone date your ex, but I wouldn't hold anything against someone wanting to date my exW when she is putting herself out in the dating pool. As J9 commented in my thread, this person is just attracted to my exW and making a go of it.
You can't turn this against a third party that had nothing to do with your M failing. If this was an affair situation, totally different story. if the person has left and you're playing legal semantics, then that's just going to wind you up. I have nothing against the guy dating my exW as my exW isn't 'cheating' on our marriage. The marriage was over long ago.