To make it short, here's a screenshot from my device:
So... JBPatch works on the Paperwhite, at least in principle.
I will be looking into this, and will try to port at least the most useful existing patches (correct hyphenation and justification*, multiple dictionaries support, ...) to the Paperwhite.
Don't hold your breath for any updates though. There won't be a full JBPatch release for the PW tomorrow, and it won't be next week either.
With the 5.3.0 firmware, thanks to Amazon's aggressive obfuscation techniques, understanding what is happening inside the device has become more difficult than ever. It's not impossible - it will just take weeks or days, instead of days or hours.
(*) Yes, occasionally, I actually do use the Kindle as an e-reader, instead of trying to break it.
