The background color for mismatched parentheses is not configurable. That's probably not a huge deal, but the color is wicked bright magenta. When using a dark theme, it burns out your eyeballs and you can't read the highlighted text.

The color is set on line 273 in basetexteditor.cpp:

 
d->m_mismatchFormat.setBackground(Qt::magenta);

I'm not sure how much work it is to make this configurable. I'm not sure it's worth being configurable. Would it be quick and reasonable to check whether a dark or light scheme is being used, and if it's dark, use Qt::darkMagenta?

There is a check for this in the method for printing:

bool backgroundIsDark = background.value() < 128;

Maybe we could change line 273 to:

d->m_mismatchFormat.setBackground(background.value() < 128 ? Qt::darkMagenta : Qt::magenta);

I'm not well-integrated enough to actually build, test, then submit a patch, but this looks like it should work.