In the Special Characters dialog, the edit bar widget displays character picks in system font rather than font family char map in use.
A problem in that system font may not have coverage of Unicode code points being selected so shows a place holder glyph.
Split from bug 97839
Presumably the "missing glyph" problem only shows up under Windows? (maybe MacOSX), seeing as under Linux the super-dooper fontconfig glyph fallback is active.
If we do want to change the font of the editbar the thing to use is probably "SetControlFont" instead of "SetFont".
One potential gotcha is that changing the font of the edit widget may change its size vertically after the dialog is active which might squash things sometimes.
Caolán McNamara committed a patch related to this issue.
It has been pushed to "master":
Resolves: tdf#100148 use the selected font for the edit area
It will be available in 5.3.0.
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.
lets try it for a while in practice to see how it plays out