See the first example in the attached testcase, compare it to the second. The first example has a slightly greater spacing between the icons, but the overall width of the grey area is the same, leading to a linebreak. I assume that if the extra spacing would be added to the width the line break would not occur. If you fix bug 304355 before this: the same applies if you have this in an :after pseudo-element. Reproducible: Always
Created attachment 72858 [details] CSS content testcase