[AviD]

It could be my line is being influenced by the results, and as I said it feels awfully weak-tight. But we have no read on the BB, would he 3-bet any ace here and CR the ace on the turn? What about some other range that we are way ahead of?

You are put in a position here where you can't check the turn because it feels so weak-tight and because there is a single diamond draw out there (which is coming anyway), but you can't call a raise. So given the range of hands, many of which you are ahead of, that may be CRed here by the BB (player dependent), I simply hate following a standard bet, fold to a CR given the board and game in question. Too many times I've been semibluff raised with a AxZd here that I am ahead of but has a redraw against me or some other random lower pair that has a diamond.

If you follow this as a default, a thinking player can pick you off here consistently and show a huge profit knowing he can get you to fold a better hand in a reasonably large pot. Of course, you too are likely calling with a diamond, so the chances decrease somewhat.

But my main question is, do you want to get bluffed or semibluffed off this hand by betting it as a default? The weight of this answer is in the player profile of BB and what range of hands he'd do this with. I would be fine betting this and folding, I'd also be fine betting this and calling down, I'm still debating if I like checking it and giving that free look to CO and BB. If they have a piece I am ahead of they are drawing to 5 outs mostly without a diamond...and coming with the diamond anyway. Checking may convince them you don't have an Ace and either get BB to bet when he would have otherwise folded to a turn bet, and CO to call being convinced you don't have an Ace and his T may be worth a call. Either way, a situation where you can get an overcall those times you are ahead and/or getting weaker hands to bet/call when they are beat and may have folded to your turn bet fearing you holding the ace.