In dark mode, selected texts are unreadable because selection background color is the same as that of text.
It might be better if selection color becomes darker, such as
I reproduce it in the environments below:
- macOS Big Sur version 11.4
Appearance: Dark, Highlight color: Graphite
How to use Dark Mode on your Mac - Apple Support
- Google Chrome version 91.0.4472.77
- Vivaldi version 3.8.2259.42
- and don’t reproduce with Firefox version 89.0 (selected texts are readable) .