Here's a great example of how this exploit can ruin the game: My friend and I were really looking forward to this game, and playing coop. Not too far in, he discovers the stealing exploit, and starts stealing everything he possibly can.
To start, it was a super boring mechanic as it is, so I am already annoyed to have to keep waiting for him (I refused to steal because I think it's a huge exploit; a money god-mode). Then, I start to notice there is no consequences to him stealing what-so-ever. None. In fact, he can steal stuff right in front of them, and barter it back to them, and they don't even notice either way.
Add to that, now he's going around with OP equipment and pretty much every item he wants, again, with no game repercussions of any type. Me and my character play by the rules, and look like fools for not using the exploit (I'm still saving for once piece of equipment I want, and he laughs at me).
And the final dominoe for me was how he just plows through enemies so fast, combat is boooooring! So for now, we are going to play the game separately, solo.
So yes, it is an exploit, a huge one, and the few people saying it isn't sound like they use savescumming and exploits in all games anyways. In every other game I've played with stealing, it is risky, you can almost never steal something of much value, and there are big repercussions for doing so also even if you are successful.
