I can't enter negative values for scroll distance in the touchpad settings, but synclient can work with them. Reproducible: Always I've selected 'general' component because kcm_touchpad is missing per https://bugs.kde.org/show_bug.cgi?id=332711
And version per https://bugs.kde.org/show_bug.cgi?id=332713
kcm_touchpad is not part of the KDE Software Compilation, but a distribution specific add on. Please report this issue to the bug tracker of your distribution.
Actually, there is a touchpad kcm product, but I am not sure, whether your distribution uses actually this one.
If it's really "Touchpad KCM" that I wrote, there's no need for negative ScrollDeltas. Instead, there are checkboxes "Reverse horizontal scrolling" and "Reverse vertical scrolling". They multiply corresponding ScrollDelta by -1.
I don't see them in 0.99 (package version 0.0+git20140305-0ubuntu1).
Created attachment 85808 [details] "Reverse" checkboxes
Ok, thanks, it's a translation bug.
It was not a translation bug either. Guess at first I was too busy searching for sensitivity and timeout settings and then I was sure I know all the settings.