Seems like they read and listen this topic, not commonly seen nowadays... One bug fixed, zillions to go! 
was:
is:
...although I would argue that favicons shouldn't overlap the separator
The suggested piece of Opera One code may look like this:
faviconDisplayWindowSize = ...; // calculate the visible part of the favicon
faviconDisplayWindowSize--; // <-- my humble suggestion ;)
----8<----8<----8<----8<----8<----8<---
The tabs are rendered in a completely illegible manner, with transparency and overlap, and without any cropping of favicons.
It completely ruined any remaining accessibility - please compare current version from Opera One vs. Opera GX. I admit I have a lot of tabs open, but they were distinguishable from each other previously, while right now it's a mess.
Why don't you test your soft on edge cases, instead you choose to go the safe path with only 3 tabs opened, with a full-screen window, and claim success afterwards?
Hope this cancer from O.O doesn't reach O.GX. If so, I honestly admit I will have to switch to Edge.
