Much and many: the opposite of less - fewer debate?

The Grammarist hints at this 'ungrammatical' usage. It appears it may appeal to young people, probably because of usage, for instance, in rap/hip hop lyrics:

Much vs many:

• There is little controversy around the many-much distinction, and it is borne out with only rare exceptions. You might occasionally encounter a much dollars or a much people, but few English speakers use such constructions out of habit.

• The distinction can be tricky in a few rare instances.

  • For example, while many thanks is more common than much thanks, the latter appears fairly often because we can think of this thanks as a mass noun (synonymous with gratitude) that takes a plural form by convention. Of course we can also think of thanks as an abbreviation of the plural noun thank-yous, in which case many is appropriate.

  • And then there are singular mass nouns that sound plural. Kudos, for one, is a mass noun that happens to end in s, so the phrase many kudos is more common (on the web) than much kudos even though the latter is more logical.

"much/little" + singular, "many/few" + plural. I don't see any cause for debate. I have never heard something like "much for continuous, many + discrete". Where did you find this queer rule?