@Xaosflux The request is to add an extra help button next to the already existing "Thank" and "Cancel", not within the existing message like I proposed on enwp. "Send thanks (help)?" was originally suggested as a compromise of the option I'm requesting now after it was pointed out that adding an extra button would involve a change in the software. But now that we know the compromise would also require a change in MediaWiki anyway, why not go for the original (and better, if you ask me) option?

What would also be nice: an ability to pre-select (or opt out) the CC in [[File:...]].

That's exactly what I meant by "like these".

@Xaosflux:

there isn't likely a good "help" target to put in to the code on this one, but if it processed wikitext projects could add their own help links

What do you mean? What's wrong with linking to mw:Help:Notifications/Thanks?

According to SharabSalam on Wikipedia VPT:

T20852 hasn't really solved this issue because you still can't play MIDIs inline. The problem is not unique to MIDI, however, because not all browsers support all of the audio formats Commons accepts, especially Ogg/FLAC/Wave/WebM. Servers transcode them into Ogg and MP3 to fill this gap but the derived files cannot be linked to via a method like [[Media:...]] or {{filepath:...}}, while {{Audio}} remains to be one of the most common ways to refer to an audio clip on Wikipedia.

JFYI, there were files with the MIME type "audio/mid" on at least jawp, ltwp, slwp, and srwp.

Purging 21 files wouldn't be hard I don't think.

Those files are all from 2006 or earlier. There are no files with "audio/mid" on Commons, for example. It could be the case that it is the MIME type of those files on English Wikipedia that needs to be fixed, rather than the MIDI conversion not supporting such a peculiar MIME type.