I thought this was going to be about how people prefer different levels of blackness for the background in dark mode. I've heard people say that pure black is more battery efficient for OLED displays (but don't know if this is true), and I know some folks prefer a less-inky grey.
I was wondering how there could be six levels though; I'd think 3 or 4 would be the most anyone could notice or care about.
for OLEDs, I tend to prefer pure black because it doesn't burn-in. Since they have a limited lifetime, any "on" time is costing me usage in the long-long-long run and I'd rather have my monitor last 5+ years than ... 2 or 3.
The more universal solution would be to standardize Reader Mode compatibility, and for browsers to let users configure how they want Reader Mode to look.
In other words, instead of an n x m solution where every web site has to cater to each different user preference, there should be a simplified content view that every web site only has to support in a singular way, and that allows browsers to cater to the various user preferences.