...if it wasn't for those pesky prepositions

This morning (that is, yesterday morning at time of going to <whatever>, my attention was caught by a charming birthday wish for Richard Wagner:

...and don't bother clicking on this screenshot, which is as dumb as can be.
Rather, give your ears a treat by going to YouTube.

<autobiographical-note subject="WCS tour, 2016">
If your YouTube experience is anything like mine (which it probably won't be) this Wagner piece is followed by a piece that Ben (the pianist on YouTube and my choir's pianist) played with us on our tour of the North-East in 2016: Abendlied.
</autobiographical-note>

You'll note that Facebook has helpfully supplied a bit of contextual information – leading me to wonder about their choice of preposition. I'm not sure what this sort of note adds.

The first response to Ben's post points to this bit of silliness on Facebook's part ...

<tangent subject="Gresham's Law?">
(not, please, behalf – although see my rant in the first update to this; the abomination has wormed its way into a kosher dictionary (Collins, I think, from memory). This seems to be yet another example of Gresham's Law as it applies to language: not Bad money drives out good, but Bad language-use drives out good).
</tangent subject>

...but, I feel, misses the point:

Facebook's note is not just otiose; it's wrong. By the same token, Oliver Twist is ABOUT Charles Dickens, that is, not.

In Facebook's defence (can I have written that? ) maybe some pictures need a bit of context-setting; and when writing a bit of generic text the right preposition in one case won't work in another. So whoever it was at Facebook who decreed We must generate some context-setting text on the fly was giving  the writer ...

<parenthesis>
(or maybe they make the mistake of leaving this sort of thing to the software engineer rather than spending money on a writer (or even, as with some enlightened and forward-thinking tech companies, a "User-Interface Engineer")
</parenthesis>

...a poisoned chalice.

That's all you're getting; a quickie. I'm thinking of more preposition-related stuff, but there's some serious tail-chasing in progress at the moment (if progress is the right word).

b