He pauses on the river, then types in chat "I'm gonna bet my flush"... Then shovels it in... I only have like 115 hands on him at 49/19 river aggression of 1...

$0.5/$1 No Limit Holdem
6 players
Converted at

Stacks:
UTG ($36.00)
Hero ($119.90)
CO ($82.60)
BTN ($86.45)
SB ($177.50)
BB ($127.90)

Pre-flop: ($1.5, 6 players) Hero is UTG+1 [Kh]
1 fold, Hero raises to $4, 3 folds, BB calls $3

Flop: [7s][9c] ($8.5, 2 players)
BB checks, Hero bets $7, BB calls $7

Turn: ($22.5, 2 players)
BB checks, Hero bets $16, BB calls $16

River: ($54.5, 2 players)
BB goes all-in $100.9, ???

Bet more on the turn.

Since he took the time to type about it, I call.

Hello, horribly played T8 with no flush.

I'm leaning towards folding because I agree with Xas' tell in that every time I have seen someone type in chat before they went to SD, they've had the nuts. Think about it this way - do you stop and type in the chat before you make a huge bluff? NO - you are scared they'll suspect something.

But I do have some comments on how you played this hand in general:

Look at how draw heavy that board is.
Now look what happens if you pot the flop and turn:

Flop: $25.50
Turn: $76.50

On the river the effective remaining stack is $43.40 so if he shoves you can easily call (although it's a crying one). Now you have an easy decision. Easy decisions in poker are +EV