Ending up in an edit conflict with two column merge turned on needs a dark mode treatment.
Some of the issues are:
- The edit buttons are completely invisible (white on white).
- Invisible text (black on black) in the help popups.
- Some places with white text on bright backgrounds.
- … possibly more?
For comparison, this is how diff and editor should look like (screenshot from the normal 2010 wikitext editor):



