How to Send Web Articles Directly to Your Kindle via Instapaper 
Just for the record, here's the master wiki page for PaperWhite fiddling:
https://wiki.mobileread.com/wiki/K5_Index#Hacks
Right now I only have two
jailbreak-related hacks.
I use
the screensaver hack to auto-display the current book as the screensaver. I looove this!
(Except when I'm reading
Vulcan Love Slave and forget to close the cover)
For custom fonts I've followed the instructions in
this post showing you how to enable custom fonts (without even needing a jailbreak).
Then since some less-useful fonts inadvertently get revealed via that trick, I hide them by installing the
Kindle Unified Applications Launcher and then
Font Config (my only custom-installed button for it) to take care of things. This does require the jailbreak.
I've played around with different hacks, but for me fonts and screensavers are indispensable!