Fix #3478: Persistent highlight is taller than transient highlight

The problem in #3478 was that when the font-size increased the font-size line-height ratio was lost. They line height should always be 1.25 times higher than the font-size so that the text would fit inside the line.

I applied the solution to the font adjustment instead of the styles, to make it possible to keep using pixels for both font size and line height. If we can change the line-height to ems, an easier solution would be to just remove all the line-height adjustments in the command function.