Comment 4 for bug 1522295

I initially thought the same; that an erratic curve sounds like a natural consequence of acceleration.

However I now think it really is just a consequence of the acceleration (2nd derivative of position) being non-continuous. Which you can see in these graphs here:

http://wayland.freedesktop.org/libinput/doc/latest/pointer-acceleration.html

I suspect if libinput used a smooth acceleration curve then there would not be a problem.