For one thing, animation cancelling adds absolutely zero dimension to Riven. It's something the Riven player can do to do more damage in less time. No player interaction, no nothing. It's like if Karthus' ult did 50% more damage if he managed to type out "pwxzcglodfxa" during the channel time.
It's not really a mechanic; it's a glitch, and she's being balanced around it like it's wavedashing
all it does is add an extra completely useless step to the process. Why do you have to click the ground in between each Q? There's no decision, only more stuff you have to do.
The least that could be done is adding it to the description, so people can at least easily understand it's a thing.
She could easily get some compensation buffs if that polarizing glitch were removed. She really relies on it at high level play