Abraham Lincoln either did or did not masturbate on his 15th birthday. But no one can "meaningfully" (in the sense in which I've used the word) say that he did or didn't.

OK, that's not the local definition of "meaningful". That explains the confusion.

there are problems with "elegance", like a lack of agreement on what it means, unless you say "elegance as defined by ..."

Well, yeah. But we can look at proofs and sort 'em into "elegant" and "inelegant", I guess, so presumably the are criteria buried somewhere in our circuitry. Doubtless inordinately complex ones.