I think what is confusing people is the "confusion" over this issue! Why the confusion? Why the insisting he's a nice guy? He's not acting like a nice guy in this - period. He's already taken this "relationship" outside the workplace through facebook, if no where else. Those are not the actions of a nice guy. What's to be confused about?
I don't get the ripping apart of the guy with the few details we have. I certainly don't get why some people are insulting and accusing the OP either. I read the the post as a guy who wanted some advice or words of wisdom for a good friend who confided in him. The guy met someone who he finds himself attracted to and he is confused about that. Maybe he has a 'romanticized' view of marriage and doesn't understand how he could be attracted to someone other than his wife. Toad is asking for advice from people with life experience to help him see what he is risking. The guy is either going to have an affair or leave his wife or choose to stay with her and be faithful. So far, he hasn't done that from what we know. All we know is that he feels something for her and that she is flirting. maybe all he needs is for Toad to tell him to defriend her and concentrate on his marriage.
The "*******" (to use the term being thrown about liberally upthread--I am kind of surprised it is allowed in the DIS) wouldn't be conflicted, wouldn't seek a friend to talk him off the ledge, and would jump headfirst into an affair.
. I've had a few friends going through their little mid-life crises and explaining the 80/20 rule is the perfect way for them to wake up and realize that what they're doing may be wrong.