How to fix missing characters from font after awakening from suspend?

This might be symptom of a kernel bug since 4.4.6, see here which reportedly got fixed in Linux kernel 4.8.x, and the fix will be in Ubuntu 17.04 (which will likely have 4.10 kernel).

On Fedora bug tracker, someone reported that changing / adding this in /etc/X11/xorg.conf.d/20-intel.conf helps:

Section "Device"
   Identifier  "Intel Graphics"
   Driver      "intel"
   Option      "AccelMethod"  "blt"
   Option      "TearFree"     "true"
EndSection

Didn't try, I am going to wait for 17.04.

To me, this happens also after switching to another user account and back.

When my Ubuntu has display problems when recovering from suspend, I fix it with a quick visit to console: Ctrl+Alt+F1.

Wait a couple of seconds if your display blinks, changes resolution etc. Then back: Ctrl+Alt+F7.