[tksb]

Interesting! I've been using this casually on iOS (via Reeder [1]) for at least a year. One thing that absolutely flips the effect on it's head (for me, personally) is the switch to "dark" mode, or simply light text on dark backgrounds vs. dark text on light backgrounds.

I suspect this is likely a typographic side-effect, similar to traditional print where dark pages "swallow" light text where as the opposite happens when inverted.

[1] https://www.reederapp.com