Hey Mr Pleno Sir
I believe I was the villain. There are a few discrepancies in the HH but the gist is as you had it. I'll post the full history the bottom of this post for sake of completeness.
This was the hand from my perspective. I've flatted the button versus an active player who's name rings a bell but who I have no direct history with (now I have twigged this is you and the bell was your username from some other thread on Blonde things make better sense, at the point of this hand you are 'new random'). I hold
Flop is middle and monotone. Pretty much a perfect flop to pick off a paint by numbers C-Bet. I have flopped a pair and may well be ahead but I'm hardly happy with the strength of my hand. You C-Bet and I raise, I'm raising here wide and expect to take down a lot of pots here while at the same time I'm planning to barrel most turns if called as there are plenty of big Spades in my range here IMO.
Turn completes four to the flush, you check. I decide to completely turn my hand into a bluff and rep a big Spade. Now I'm not completely happy with my sizing here. I think I can shave 150-200 off the bet to do the same job. I've been hefty here to try to fold out some weaker spades (tens with

etc). The 'new random' gets a little sticky with these marginal holdings and I'm trying to exert a little extra pressure. As a 'new random' when you call here you either have the very top end of your range or you're a bit of a caller and will most likely call any river bet. Also if you call the turn you pretty much have to call that river. I'm flying the white flag at this point.
As to if you missed out any value, I don't think so. I don't like leading the turn for you if we have no direct history. From your description of the table I assume you have me down as a bad player so you might think I get stubborn with weaker spades and will call/push with a set and hope for a pair up. Maybe leading the turn is profitable if you know the player will do that but you can equally think that a bad player will bet

up for value on the turn and river or at least check turn to call a bet on the river.
Maybe a little tickle on the river to essentially annoy me might squeeze out a little extra value from worse flushes or even induce a stubborn jam from a bad player but without history I'd much rather check to allow the bluff to continue. I can complete the bluff and in this case spew off but I decided it was a little early in the MTT to do that.
Addressing the comments by Muckthenuts, genuine question, while I would never say this is a hand to tell the grandchildren about, what from this hand makes me 'obv bad?'
Sky Hand History 445663035
Blinds 20/40
Table is 5 handed
Santoon (UTG playing 4700) raises to 120
TommyD (BTN playing 8K) calls
Blinds fold
Flop

Pot 300
Santoon bets 150
TommyD Raises to 400
Santoon calls
Turn

Pot 1100
Santoon check calls 800
River

Check Check
Santoon

TommyD
