In D22647#500117, @ngraham wrote:

Whoa, huge diff. All the more reason why we need to find a way to have all the icons use a single external stylesheet.

This will require documentation changes as well on https://hig.kde.org/style/icon.html and https://community.kde.org/Guidelines_and_HOWTOs/Icon_Workflow_Tips

As for the change itself, this is what happens when using the light color scheme:

Seems like this change just shifts the problem from Breeze Dark to regular Breeze.

Actually, the problem isn't shifted at all, the change just doesn't fix anything for the current versions of Breeze and Breeze Dark. I'm using a custom colorscheme that reflects how I want Breeze Dark to look in the future. Breeze will use colors like these in the future:

Right, I see that there's actually no regression. In principle, can you describe what a color scheme needs to do to avoid this situation?

In D22647#500137, @ngraham wrote:

Right, I see that there's actually no regression. In principle, can you describe what a color scheme needs to do to avoid this situation?

Use a selection background color that is different from the button focus decoration color.