Giant, something Im wondering about. Several times you refer to the work situation. Is there something more than you two merely working at the same place? Are you his supervisor? Do you outrank him? Are you much older? Are you his senior in any way?
I understand that we gay guys can now get married, and so rules against co-workers marrying may apply to us. That said, to most of your co-workers, it must appear that you are just a couple of work buddies maybe having a bit of a man crush on each other. I wouldnt expect any co-workers to think that would be inappropriate. If something were to get started between you, whos the wiser until, and unless, you become an apparent couple.
But of course, if your work relationship is such that you outrank him materially, that would be a big issue.
If not, ask yourself why you are bringing it up so much; it seems to me that you are trying to make an impediment when none exists.
Another thing, you said he isnt married, but I did you tell us whether he has had established -relationships with women. Depending upon his age, assuming hes right hot looking, if the guy doesnt have a girlfriend, been in a couple relationship, at least got a gal-pal fuck buddy, why would that be?
In fact, when he isnt socializing with you and your co-workers which you have described what do you know about his social life? From what Ive read and my impression [of course, Im gay and rooting for you] he might be flirting with you wishing something would get started and afraid you will reject him.
OK, now lets consider the devils argument. My experience has not been good with these things. Im better off trying to make time with guys I know are gay; even if I get rejected, its not embarrassing. I have a couple times mistaking being courted as an older, more established, maybe more financially secure person by an ambitious young man figuring I will help him thinking he is making a sensible move only to experience disaster when I let on that I am responding sexually to his courting me.
So thats one more thing to consider. Are you sure hes flirting and not buttering up someone whom he hopes will be his mentor.