How will it make you aware of uncertainty? At some point you do have to guess (called "estimating" here), do you not, and that will have a compounding effect on the outcome. You incorrectly guess a probability somewhere only by a small amount, and it multiplies its way through to the result, and you're looking at a potentially huge difference in resulting probability, which could easily span the "will act" or "won't act" gap.
I think it's worth keeping the principles of bayesian reasoning in mind. The idea that you should update hypotheses on evidence, and adding probability in one place takes it from everywhere else slightly, keeping track of prior probability, etc.
Not that you should actually do mental calculations on made up probability estimates. I mean you can do that, and if your estimates are at all decent, the result might be better. But I don't think anyone actually recommends that.
But in general, no one has enough computing power in their heads to go and do explicit bayesian updates on everything all day long. You have to pick your battles, and use the right tools for the task at hand.
That post is like nobody there has ever heard the phrase "don't fall in love with your model".
Quite a lot of LessWrong posts are of the theme "my model gives this counterintuitive result" - the trouble is they go on to "AND THIS IS VERY IMPORTANT AND SIGNIFICANT!!" rather than "hmm, maybe my model needs work."
