[FoxwoodsFiend]

Jon is a VERY tight player who is not afraid to make tough calls and he can be tricky at times. So while he is not a typical nit, cold-calling a raise out of position with anything but a set or two pair here is still almost impossible for me to imagine.
The one scenario in which I think this river move makes sense is if John decided to play JJ this way, which while not inconceivable is still very improbable.

Also, don't think that his less than pot-sized bets are signs of weakness-he makes these sized bets with strong hands all the time. I don't think he would call with a draw on that flop either. If you did somehow manage to get John to fold you got very lucky, and from playing with him on numerous occasions I can tell you that running bluffs into him when he's been giving action is not a +EV decision.