I was raising two things where the style settings have no effect:
In the game record window, I have seen no effect from font settings -
I tried putting in an italic font - font_name="Lucida Italic 12" in
every style in .gnubg.gtkautorc. The labels on the board, analysis,
commentary and messages windows all show up in italics. The game
record window is still in the original font. However, the styles
setting colours for errors are taking effect.
The second issue was the selected move in the analysis window - the
line for the move actually selected is in the highlighted colour, but
not in the italicised font. I understand that this is a result of the
ancient highlighting code.