This bug's simple and short to explain. In mobile view:
- Submit an edit on a post. Provide an edit summary for your edit.
- Return to edit that post further within the grace period.
What should happen: The edit summary should be prefilled with the one you just provided, like on the regular site view.
What happens: The edit summary will be blank.
(That's it, that's the entirety of the bug.)
This leads to an additional quirk
As for what your edit summary will actually wind up as in the revision history, something different happens depending on whether you filled out an edit summary in mobile view or not:
- If you submit any edit summary at all, it will overwrite your previous one.
- If you leave it blank, an autogenerated edit summary will be appended to the current edit summary of that revision. This will repeat indefinitely for each edit within the same revision. Here's an example of this in action.