"Dates Without Prepositions (or: The Punctuation of Henry Adams) 1 November 2003 Henry Adams' histories of the Jefferson and Madison ... into the narrative as a sort of parenthesis, with no proposition at all, but usually with a comma or two."
Some American jouralists use days of the week in the same way, e.g., The president returned to the White House Tuesday. We had a thread about this phenomenon a while ago.
"Two questions: (1) Does any other author make a habit of this?"
The historian Will Durant surrounds his dates with parenthesis:
Cicero returned in triumph to Italy (57).
This is not nearly as offensive as the inline style.
"(2) Considering how peculiar the usage is, how does Adams get away with it? Why does it seem only slightly odd and not flagrantly wrong?"
The date, which ought to be a noun, has effectively become an adverb. It has a cheap, journalistic sound to me. It's like if I had omitted the "the" from the last paragraph, and just written "Historian Will Durant".