The bug

The new accessibility feature, Text Background, applies a background even to text pieces that already contain a background normally; this causes them appear darker than usual. Since they already have a background, I'd expect them to stay the same with the feature enabled or disabled, not appear darker when it's enabled.

The only places affected by this, as far as I have noticed, are the sidebar, the subtitles, and entity name tags. Note that this is NOT the case for the debug screen, which always stays the same. If the darker background is intended, then there's an inconsistency either way, as it should also apply to the debug screen.