Whilst reviewing and discussing this
for weltschmerz I found out that there actually exists a global property
that is honoured by all applications that build on GTK.
I don't think I've ever seen this exposed in a settings dialog. Perhaps in the
accessibility settings, I rarely venture there. In any case, you can put
properties like these straight into
~/.config/gtk-3.0/settings.ini and GTK
apps will pick them up.
For QT apps it seems you can set
to a negative value in the aptly named
~/.config/Trolltech.conf but I could
not get this to work with the only QT app that I use, quassel.
Not that I would want to, I do prefer a blinking cursor.