Thanks for the response, LyricLover. Mine looks the same as yours.
Which got me wondering why it writes to ARTISTSORTORDER rather than ARTISTSORT, and I think the reason is this
While I suppose one option is to try to change the Column, my music server understands this particular tag names, and I am worried about downstream collateral damage. Also, this is far from my only customized fields that my music server uses to build out menus specific to the way I like to listen to music, and they all exhibit the same behavior. Is there some way I can edit arbitrarily-named tags and still see them in the tag panel?