[mike l.]

"Perhaps villain usually calls with ace high and worse, but bluff raises often enough for a call to be good. Is this so hard to imagine?"

that's not at all hard to imagine but it's part of what makes a bet-call here awful. if derb bet-calls here it means he's playing by the seat of his pants: he doesnt have a plan for each street, he just reacts when presented with the consequences of his most recent decision. that's how donks play. because of the one card straight on board and the Q on the flop and the fact it went to 3 bets preflop it's correct for derb to bet if he gets called enough by A high or worse pair, OR it's correct for him to check and let cutoff bet if he's the type to bluff a lot. but it's not both ways. there are other boards and other scenarios where it can be both but this is not one of them. if derb had something like TT then this might turn into a bet-call scenario depending on the opponent. but for derb to bet-call this board means he is playing on the fly and while his instincts may be good at times due to experience, he's basically a donk.