Your reply sounds a bit fishy. Your second sentence "he doesn't explain why his advice is worth a damn" is inconsistent with a rhetorical question.
I agree he doesn't have much cred by the way, and his method is nothing new or special. But I think his advice is generally sound for an uneducated player who wants to improve.
I actually phrased my comment in the style of a marker who is marking some academic work, like an essay. The norm here is to address your points to the content of the paper itself and not appeal to outside information.
So my comment is more clearly saying, "This essay would be stronger if you used evidence or authority of some kind to back up the assertions you are making." This is actually a polite way of saying "You don't know what you're talking about and shouldn't be proclaiming yourself an expert on this topic."
I agree he doesn't have much cred by the way, and his method is nothing new or special. But I think his advice is generally sound for an uneducated player who wants to improve.