I noticed that overline text is not as configurable as underline text. Using x-underline-at-descent-line, it is possible to choose between placing the underline at the baseline or the bottom line (I think the naming of this option is not quite right.). However, it is not possible to choose between placing the overline at the ascent line or the top line. Instead it is always at the top line. This makes overline very ugly when the height of faces differs on a line because the overline will appear at the very top of the line instead of on top of the font.

It would be nice if there would be an option x-overline-at-ascent-line which places the overline at the ascent line (instead of the top line).

Ideally, there are variables x-underline-position and x-overline-position which can take values bottom, descent, baseline and top, ascent, respectively.