It doesn't seem as if there are any ill effects on older Kindle models/firmware but just as a precaution:
DO_FACTORY_RESTORE was what ended up completely bricking one of my PW3s after I tried downgrading to factory 5.8.9.0.1. I think it failed at reformatting /mnt/us (
user
store). After that, I no longer had USB mass storage access (and I didn't wanna mess with opening the device for serial).
https://www.mobileread.com/forums/sh...&postcount=116
https://www.mobileread.com/forums/sh...d.php?t=275975
In my case, I probably should have just installed customer 5.8.11 when I saw the corrupted the display.