If count nouns required “fewer”, as some pedants claim, then < would be called the “fewer than sign”. But so long as the statement “four is less than ten” is correct, I maintain that “four items of groceries is less than ten items of groceries” is also correct, and that therefore the person in the express lane with four items may be said to have less than ten items.
No worries; as you say, the great thing about this board is the way it constantly leads to learning new things.
Someone else around here gave this example of how “less” is correct:
10 Items or less [than that amount of shopping]
Yes. I did in post number 14. 
Hear, hear!! <banging on tables and enthusiastic waving of cigars>
You know, I could care fewer.
“Couldn’t”.
I agree that in the example “10 items or less/fewer”, either is perfectly correct depending on how you parse out the sentence. On the other hand, if an add for a mortgage company says they will give you a loan with “less hassles”, it just sounds wrong to me. It isn’t because I’ve been taught it, at least not that I remember, it’s because it reflects the usage to which I’ve been exposed, in contexts where correct usage was expected.
One problem I have with with careless misuse in situations such as this, is that the effect is ultimately to combine two words, formerly understood with distinct meanings into an interchangeable pair of words that have the same meaning. Flaunt/flout, compose/comprise are additional examples of this. Losing fine and not-so-fine distinctions between word meanings is not in any way desirable.
How do you know it’s necessarily prescriptivist propaganda? Yes, I know that somebody tried to get everybody to use it a couple of hundred years ago, but he essentially succeeded, and to many Anglophones today, the fewer/less distinction is necessary and correct. In debates over usage there are always those who assert that however people want to speak or write, is fine, but how do you decide which distinctions and rules are necessary and which ones aren’t? The natural grammars of all languages have some markings that are redundant. They serve to ensure the conveyance of meaning. Does German “need” to have five different ways of saying the word the? Probably not, in some contexts; a foreign speaker of German can often still be understood if they use the wrong gender or case. But the case markings are still there. Just because sometimes, or even most times, it’s possible to violate a usage rule and be understood is no reason to assume that the rule is unnecessary.
My easy way to remember the less/fewer argument is simple:
Fewer cookies, less pudding.
Fewer pennies, less of anything. 
My own ears are such that I generally wouldn’t say “less hassles” or “fewer hassles”, preferring to say “less hassle” (i.e., taking “hassle” as a non-count noun). Google seems to back this up as by far the most popular of the three. Are you sure it’s not something about the word “hassle” in particular, and the ambiguity over whether to take it as a count noun or not, which is influencing your judgement here? (I.e., if an ad for a mortgage company says they will give you a loan with “less forms to fill out”, will it sound just as wrong to you?)
Of course, my argument is grounded in the fact that the “distinction” being lost is not one which is or has ever been widely naturally followed, so there’s not really a loss. (That having been said, there will continue to be the following distinction, either way: “fewer” cannot be used with non-countables. No one disputes this.)
My standard of evidence would be empirical studies of the usage of actual speakers, which, to the best of my knowledge, come nowhere near supporting modern widespread adoption of the proposed “less”/“fewer” distinction as a native English norm (certainly not on the level of “‘Less’ is verboten for use with countables”).
I propose nothing but that native speakers of a language are free to employ their spoken language as naturally comes to them; rules need not be imposed extrinsically. People who have never been exposed to a whit of formal education get along speaking perfectly fine. (As for written language, there are some more rules there, it being a less natural human activity, but certainly, where the issues present overlap with those of spoken language (such as in matters of syntax, word choice, etc., as opposed to spelling or punctuation), there is no need to straitjacket it further).
But I’ve never said the standard is “be understood”. My standard is “speech in the natural manner of a native speaker is perfectly cromulent.” I can easily accept that there are sentences which are readily understood and yet thoroughly ungrammatical (say, “Please, bathroom where to the can find I would like some?”, whose intent is readily grasped, and yet no native speaker would ever straightforwardly utter it).
“<” is called “less than” because in a mathematical context, those become real numbers, not discrete quantities. Four is less than nine point one. I suppose you could say “five is fewer than eight point seven” but that sounds very weird to me.
*** Ponder
Well meanings get lost in time, and English changes, so I don’t think one can correctly say anything is wrong.
Obviously we don’t talk like we did in the 1600s or before then. But that doesn’t make all our speech now wrong.
It’s like the phrase “Hopefully it won’t rain.” That’s wrong, because hope implies aspiration, and one can not aspire to making it not rain. One can say “Hopefully I’ll be a good dancer,” because one can aspire to become a good dancer.
Yet I don’t think anyone except an linguist Nazi would say “Hopefully it won’t rain” is so incorrect it shouldn’t be used.
“Hopefully” used to be considered wrong by some (and some still consider it non-standard, although I think it’s standard) because they insist “hopefully” is an adverb that’s supposed to modify a verb (meaning “in a hopeful manner.”) They would say that the word is only used correctly in sentences like “Hopefully, he looked up at his mother.” (In this case, “hopefully” modifies the verb “looked.”)
I’ve never heard an objection to it because of hope implying aspiration, or anything like that. It’s its use as a sentence adverb that some critics object to. Oddly enough, these critics don’t seem to object to other sentence adverbs, like “frankly,” “apparently,” “certainly,” or similar.
There’s a difference between a number and a number ***of ***something. The number 5 is less than the number 10, but 5 apples are fewer than 10 apples.
Could the whole controversy not be circumvented bu substituting “Under” and “Over”?
Mine’s the asbestos one