Villain in SB is a rakeback/tournament freeroll grinder who plays a lot higher than this, but spends a lot of time in the microstakes as well. I haven't seen them do any of the obvious actions that flag a dunderhead (call the blind first in, coldcall two or more bets, donk the flop, etc.).

Winning Poker Network (Yatahay) - $0.50/$1 (6 max) - Holdem - 5 players
Hand converted by PokerTracker 4

CO: 36.35 BB (VPIP: 62.63, PFR: 20.68, 3Bet Preflop: 10.29, Hands: 934)
SB: 100 BB (VPIP: 40.74, PFR: 31.85, 3Bet Preflop: 18.37, Hands: 135)
Hero (BB): 28.73 BB

SB posts SB 0.25 BB, Hero posts BB 0.5 BB

Pre Flop: (pot: 0.75 BB) Hero has 4 2

fold, CO calls 0.5 BB, fold, SB calls 0.25 BB, Hero checks

Flop: (1.5 BB, 3 players) 8 5 3
SB bets 0.5 BB, Hero calls 0.5 BB, fold

Turn: (2.5 BB, 2 players) K
SB bets 1 BB, Hero raises to 2 BB, SB calls 1 BB

River: (6.5 BB, 2 players) 4
SB checks, Hero checks

I had been planning on firing on the river -- 42 is the nut low hand -- but I caught a pair on the very end.

Checking behind here is standard, right?

I think it's too thin to value-bet, and I don't think he folds anything better, so check. Maybe he had 64 and you lose on the river, but whatever, checking is what I would do.

Betting here would be pretty bad IMO. Check and beat hands like A3 or busted hearts sometimes. Fire it in with your Th7h hands.

why do you think semi bluffing the turn is better than calling?

my initial reaction is the pot is too small and your hand is too good for this line. you can't fold to a turn 3b and there's no showdown value so you're going to have to barrel the river on blanks to fold out missed flush draws

I'd like this a lot more with 97o for example

I like the turn raise on occasion; as long as it's at low frequency relative to the other more powerful semibluffing combos that are plentiful in your range.

I'd check the river and expect to win sometimes.

If I don't improve, as I said, my hand is the nut low, guaranteed to be included in my river bluffing range. Barreling the river is an essential part of the plan.

interested in hearing thoughts on flop raise vs turn raise.

i like checking river also as we now have show down value.

I think this line is fine and probably good as long as he's not going to 3b turn very much.

Agree checking behind river is super standard

As played I think checkback is fine, also think it would be ok to fold flop with a player behind.. i don't think implied odds are particularly good here

I think the read on co after this action:

becomes "loose passive until proven otherwise."

So getting rammed on the flop is not a concern imo. If and when we actually get rammed on the flop? Our implied odds are pretty good on later streets because loose passives have good hands when they jam flops.