Earlier quoted context omitted.
Ditto. I was also zoomed at 150%, zooming in to 100% makes it go away. Still worth fixing if possible, since many users browse at non-100% zoom.
> "many users browse at non-100% zoom" This sounds dubious. Do you have a source for this?
For anything with a higher DPI (including UHD/4k, but also lower resolutions), zoom is required to be able to read the text on most pages.
I run with 125% zoom on the 5+ year old iMac I use at work, and it makes a big difference.
If you'd like to see what size the fonts are with 100% zoom on a UHD monitor, try setting the zoom to 50%. You'll see.