Ending a sentence with a preposition

"It was once a cherished superstition that prepositions must be kept true to their name and placed before the word they govern . . . . The fact is that the remarkable freedom enjoyed by English in putting its prepositions late . . . is an important element in the flexibility of the language."

H.W. Fowler, Fowler's Modern English Usage 473-474 (2d ed., Ernest Gowers, ed., Oxford 1965).

(Fowler was writing in the 1920s, by the way.)

Under this supposed rule, we get sentences like this:

• I am providing a copy of various university regulations of which you should be aware.

Why not "that you should be aware of"?

Check any source on English usage. All that I have checked say essentially this: End a sentence with a preposition if avoiding it would sound awkward or pretentious.