MikeC -“There is someone who both parties are culpable to. This makes them less likely to sin.”
Oh yea, of course. Just like Yoseph Hatzaddik had the image of his father appear to him. Can you just picture it, you want to sin and the image of your Shadchan (I’ll leave the description of her appearance up to your imagination.) suddenly appears and invokes the fear of G-d into you.
I really don’t think so. If you’re the type to do Aveiros on dates, then it won’t make a difference if you were set up by a Shadchan or not!