Hard disagree; it's not a useful comment precisely because it's prescriptivism. It's suggesting people are incorrect because they're using a commonly accepted meaning of a word, that's just not how language works.
Edit: Perhaps I should be clearer. The "less vs fewer" rule was invented roughly 200 years ago and doesn't actually hold true, "less" has been used this way for far longer. It's the epitome of "I want English to work this way, fuck everyone else".