When tight players raise it is very unlikely to be a bluff. When loose players raise, it is much more likely to be a bluff. Balanced players will work in bluffs with the right combinations of hands and are the hardest to play against. That being said, I don't think you can ever consider folding KK on an AK7 board, even against the tightest players, that's just a cooler.
I agree with the possibility of bluffs against you. There is a reason that raises and check-raises are usually viewed as strength, but naturally: some players will use these tools as bluffs. For "solid" players though, this is rarely a bluff. They must be
bluffing less than they have it or they wouldn't be as successful in poker, long-term, as they have.
I have mixed feelings against folding KK on an AK7 board, even against tight players though. You are correct, most every time we are continuing even against tight players or nits. We just flopped a very strong 3 of a kind and these cases don't come up often enough to just pass on. When I get a strong feeling though, I will sometimes have to discipline to fold this hand. I know easier said than done (and even then I hate folding 3 Kings here because it is such a great hand), but I have good confidence in my intuition and spotting reliable
tells. 99% of the time I am probably playing this hand further though; they simply have very low chance of pocket Aces/beating us, and even then you could just call it a cooler, but I like to minimize even coolers if I can; maybe I trust my gut reads more than the math
odds sometimes (for better or worse), but this approach has served me well thus far.
