When editing this question by replacing the supplied images of the formula with identical mathjax formulas I tried to supply a reason as shown in the image with "use mathjax instead of images". However that edit reason was declined by the system with a message of
Comment reserved for system use. Please use an appropriate comment."
I actually tried a few variations of the shown comment, but none was satisfactorily until I deleted the edit reason and left it blank. This happens identically here on SO meta where I cannot fill-in any edit reason whatsoever.
Giving an edit reason is not mandatory, but might sometimes be desirable. However I wonder whether I miss here something?
If not, I'd like to suggest to change this check so that usual reasons can be given and differentiate system reasons (if needed) differently.
Lol. And after reviewing, when posting this very question in astronomy meta or here in meta, I get repeatedly a 404 when hitting the "post question" button. Something seems to be fishy right now.