This is Reuben's hand 5, and he plays it rather differently than I would. So, I wonder why (I'll also try to post one showing how he plays the nut flush, as I have questions on that one, too). Here's the hand:

He limps UTG with KhKd7c2h (5/5 game). Unraised pot with 6 players seeing the flop, which comes Jh8h3h, making Reuben the 2nd nut flush.

Checked to him, he checks, and that's really my main question, as he also thinks that's a much better play than leading.

I'll first give what he considers the best line: He checks, LP (good player) pots, he calls, all others fold. Turn 6s. He again checks. LP pots again. Now, Reuben thinks the best line is to fold here against a good player, but in reality, he calls and considers that at least not be a very bad line (he gives these ratings for various actions: folding here gets a 10 and calling gets a 7).

Finally, the river is 3d, pairing the board. Reuben bets 2/3 pot, repping the full, but considers checking to be a better line.

Ok, so Reuben thinks the best way to play this in a 6-way pot is to check-call the flop, then check-fold the turn. I'm rather uncertain whether I like this or not.

Anyhow, against the Stars 1/2 field, I'd generally take another line, which I'll try to analyse for purposes of comparison: I'd bet it out on the flop.

If I get raised (and a lot of players will raise the nut flush, although that's probably not such a great line), I can easily fold immediately, although they can of course also be making a naked A bluff.

If I get called, then they should have: 1) the nut flush, 2) a lower flush, possibly with straight flush draw (like Th9h), 3) a set to which they're drawing, really at a bad price, or 4) the naked A with the intention of bluffing (although the naked A would probably raise). I'd probably then check-call the turn and check-fold the river. If the river had been a blank, I don't think I'd be able even to call half-pot.

I'm rather confused here, as there's actually no line that I'm completely happy with against good players (and with that I mean capable of betting less than the nuts but also not absurdly bluffy).

Maybe Reuben's passive line is best. The real fear on a flush board is a full (to some extent straight flush, although those are long-shots), and the probability of filling up on the turn is low. Moreover, it's pretty risky for an LP player with JJ here to bet out the flop rather than just take the free card.

But one MIGHT want to play flushes like this: Check-call the flop with any reasonable flush (including Q-high but that's about it, maybe also with straight flush open-ender). Then check-raise the turn with the nut flush??

Also of note is that there are 6 players seeing the flop here. With 4 players, it seems to me like check-folding the turn is rather on the weak side. There, I'd be tempted to just call LP down all the way to the river with a second nut flush (?), depending somewhat on just who the player is. For that line to be sound, they have to be capable of betting a loser all the way to the river anyway.

With 4 players, I'd also almost definitely bet this thing out unless LP is the type of player who is more than likely going to bet (?).