Not sure if it would be useful to anyone (it was very useful to me, as I'm using my Hisense A5 was an e-book reader only, without all the telephony functions):
If you run the command
service call epd 4
It puts the device in a "force refresh" mode when every update of the screen triggers a full re-draw.
This means that every page turn in your favorite reader app will be a rad slower but 100% free of artifacts.
Hope this benefits anyone (like it did me
)