As shown in the past, I'm perhaps a bit too obsessed about finding Easter eggs on Hubski. That's because I know they are there, and once more I got a proof that "the truth is out there". ;)
Go to any post. Literally any will work, but here is a one chosen at random with a simple python script. Nice feature request from about two years ago.
Now, check this out!
Look at the addresses. Simply switching /pub/ to /print/ makes it printer-friendly. :D
However, this also comes with a minor bugski: it's not listed under robots.txt so it could be abused in some way (and also a reason why I didn't find it much sooner). I have confirmed that it can't (EDIT: thanks, cgod! Just for the future reference - the negative was here, I'm making it bold to avoid misreading-related problems) be used to, for instance, read someone's private messages or deleted posts/drafts, but I do feel that 'forgotten' features like this one could use some attention.
EDIT: It doesn't seem to work any longer. Bit shame, but it's perhaps for the better.
EDIT2: And now it works again? Stop messing with my head! :P