When editing a Discussion Post (or an issue/PR comment? Didn’t test it on those) does the Dark theme break partially.
The area with the edit options (bold, italic, Write and Preview tab, etc) will be in a blue tone, while your name will remain with a dark grey color, which looks extremely out of place and is made worse by the fact, that your avatar is partially within the blue area.

Example image:

image936×241 11.2 KB