There's different sorts of criminal activity that you CAN get away with in game.
A complex con-artist job where you convince someone to give you all their valuables and then vanish? Yeah, that's cool, adds to game. Do this in the League, very Locke Lamora, they'll love it.
A concealed and devious series of acts of malice and treachery, to bring down and spite those around you? Yep, been done with great flamboyance (House Lusignan of Dawn. The villains really were the ones in the black hats....).
Randomly mugging someone in a dark bit of Anvil, grabbing everything they have on them, and then legging it into the night... well, you could. The militia will get some fun from that and you'll be hunted down like a fox. Could work as the ending of a character driven to desperation by love/debts/addictions....
Opening other people's tents, having a rummage around and walking off with anything that looks vaguely IC.... No. This is against the rules of the game, and the social contract. Deeply uncool. We don't want to have guards on our IC tents, we don't want to have to chain down everything, and we don't want you coming in when we're having a snooze.
(80% of the way down, IC theft)