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Among my mother’s circle in Brooklyn - back in the fifties and sixties - one would say ‘Mention by you’ in response to some kind of congratulations, meaning, I think, ‘May you be similarly blessed’.
Ever heard anything like this?

First, No, I haven't heard this expression.
Second, is there a typo in this? Did your mother say "mention by you" (as quoted) or "mentioned by you," with a past tense -ed? In latter, the syntax seems to me to reflect the semantics/pragmatics of the situation.
Third, in pragmatic terms, the expression seems similar to "So who's counting?" a sort of passive - agressive phrase meaning something like "Why did you bring that topic I shouldn't brag about up for?"

Thanks, bnj. No, I wrote it as it was. And I’m certain there was nothing negative in the intent.

Apropos of nothing at all . . . but I just ran across a line I copied from a novel. I think you’ll appreciate this:

“ . . . and that if I wasn’t careful, I was courting disaster - or at least asking it out on a first date.”

All the best.

Nice line. What novel was it in?

Hi. I’m pretty sure it was one of the Longmire novels by Craig Johnson. He also wrote something quite like “ . . . gray hair framing a face carved from hard wood, with a dull chisel.”