Sometimes community mods set their community-specific themes to something that is entirely unreadable - like dark text on top of a black background for a spoiler box, itself on top of a light-colored background (where the dark text would have been readable, except the spoiler box changing everything). I am having to turn off community theme overrides entirely as a result if I want to read the content.
One suggestion could be to provide a link to an external testing tool, or better yet put some automated testing directly into the code where the community themes are built, to alert people to such accessibility considerations? Honestly the latter might be more work than strictly necessary... but it also sounds kinda fun so I thought I would mention it 🤔🤣.
