Comment 3 for bug 1635361

It seems the problem is made by switching to "libinput"; Since it was not existed in Freya, and there are other reports by people from other distros (e.g. Arch) switching form synaptics to libinput, having exactly the same problem.

Although the problem might be in libinput, performing some patches to control the sensitivity, or switching to another replacement for libinput should be considered; Since the touchpad is unusable in the current state for many users.

By "patch" I mean something like synaptic's noise-cancellation feature.