I think there's some confusion here as to what the utility function is defined over. And to be fair, the post itself is somewhat confused in this respect.

The argument that it might be more or less rational to gamble is an entirely different matter to whether it is more or less rational to smoke crack.

The shape of the utility function over money can make it more or less rational to accept particular money gambles: risk aversion is after all a property of the shape of the utility function.

The shape of the utility function over money cannot affect whether specific, non-risky choices about how to spend that money (e.g. whether to smoke crack) are more or less rational. If crack is you best option, that's already reflected in your utility function for money; if it's not, then that too, is already built in.

NB: This comment is not as precise as it should be in distinguishing decision-utility, experienced-utility etc. I think the fundamental point is right though.