Running KDE Neon. Discover is already the newest version (2.1.2-7ubuntu1). Scrolling with touchpad get hyperactive and continues moving in high speed after lifting fingers even with coasting off in touchpad settings.
I haven't seen this. Which Neon version are you running?
Created attachment 105239 [details] Screenshot of About system
Fresh install from neon-useredition-20170420-1126-amd64.iso. Same issue with the image from a few weeks prior.
I can confirm this on Arch.
This was fixed in Kirigami, will be in its next stable release.