Personally I never do it, and I don't think I have the discipline to start. There aren't many situations where I'm in between check calling and bet calling/reraising. Explanations?

if you haven't you should start. Bet folding a lot of times has better +EV then check/calling on a scare card on the river.

For example if you are up against a passive calling station then bet folding on the river would be a very good idea cause his raise would for sure interpret that he has you beat. And you get value out of your hand if he doesn't have your hand beat but calls anyway

I use it rarely.
I think it's exploitable.

However, I will do it with the 4th card to the flush on the river against a straight forward/passive player.

ClarkMeister. I think.

Or OOP with Ace high HU against a passive who might fold or call with worse.

I think it's very rare you'll be up against someone who:
a) notices you take the bet/fold line too much
is sophisticated enough to use this info against you

OOP against a passive with ace high is a check/fold, not a bet/fold.... i mean, unless you literally see him calling down every time with anything.

oh yeah.

sht.

I'm kinda out of it.

In a big pot I will Bet/fold Ace high against a passive.
Not against a really loose player, but a passive who calls dwon with bottom pair but could fold it UI.

Look, I call with 3rd pair on flop, and maybe on the turn with odds, and then fold UI on the river if the bettor has shown down solid hands all night.

why can't others fold pairs on the river?