Ok, I copied text that was visible in both dark mode and light mode. When I pasted it while in dark mode, it became invisible, and after moving back into light mode, it is still invisible.

I tried to edit while in dark mode, and what I was typing, I couldn't see.

So Greg is correct, there is a problem with dark mode.

EDIT: even more strangeness, in my previous post, now the "E" where I tried to edit but couldn't see it, is visible. But only visible in dark mode.