Comment 19 for bug 790130

Ahh, perhaps we're on to something here: I noticed that if
I choose e.g. the "Echo Icon Theme Palette" instead of using
the "Inkscape default" palette (by clicking on the tiny palette
selection arrow just to the right of the palette rectangle, which
is the thing just below the drawing area), then the pen pressure
works fine! I can even select various colors for the squiggles I've drawn.
But if I go and choose the "Inkscape default" palette, or the "Greens"
palette, then the pen pressure is gone forever (at least until I switch
back to the "Echo Icon Theme Palette", and restart Inkscape.
This might be a more tractable bug for the Inkscape developers
to look into (assuming they can reproduce the behavior on some
pressure-sensitive tablet).

The "Inkscape default" palette corresponds to either
  /usr/local/share/inkscape/palettes/inkscape.gpl
or
  /usr/share/inkscape/palettes/inkscape.gpl
depending on whether we're using the build-from-source
or the Ubuntu package, respectively, which was why simply
removing the entire "palettes" directory brought the pen
pressure back again.