After receiving my brand new XPS-13 with Ubuntu 16.04 the first thing I noticed is that the palm rejection feature is not present at all.
I will try to describe as best as I can the methods I have tried and whether or not they were successful.
I tried was was suggested here and installed:
sudo apt-get install xserver-xorg-input-libinput
Then I edited the file /usr/share/X11/xor:g.conf.d/90-libinput.conf so that it contained this:
Section "InputClass"
Identifier "libinput touchpad catchall"
MatchIsTouchpad "on"
MatchDevicePath "/dev/input/event*"
Driver "libinput"
Option "Tapping" "True"
Option "PalmDetection" "True"
Option "TappingDragLock" "True"
EndSection
This method was not succesful at first. A little tweak was needed. If you list your /usr/share/X11/xor:g.conf.d/ directory you may have a 51-synaptis.conf file. That file takes precedece over the libinput one that was just created. To solve this problem make a symlink with a smaller number:
sudo ln -s /usr/share/X11/xor:g.conf.d/90-libinput.conf
/usr/share/X11/xor:g.conf.d/40-libinput.conf