Button looks extremely fishy

PokerStars No-Limit Hold'em, $0.50 BB (9 handed) FTR converter on zerodivide.cx

CO ($20)
Button ($9.10)
SB ($53.60)
Fnord ($51.75)
UTG ($90.85)
UTG+1 ($12.20)
MP1 ($56)
MP2 ($33.45)
MP3 ($8.50)

Preflop: Fnord is BB with 4, T. CO posts a blind of $0.50.
5 folds, CO (poster) checks, Button raises to $1, 1 fold, Fnord calls $0.50, CO calls $0.50.

Flop: ($3.25) J, 3, 4 (3 players)
Fnord checks, CO checks, Button bets $0.5, Fnord calls $0.50, CO folds.

Turn: ($4.25) T (2 players)
Fnord checks, Button bets $1.5, Fnord raises to $8....