I don't know how kosher this is for online forums and whether there will be green-erds cringing, but how about adding a feature to be able to print a question/answer or even an entire discussion? Of course, over on Math.SX, LaTeX formatting is interpreted to present mathematics (via
MathJax) as graphics in order provide a nice graphic context. But we also upload our own images (LaTeX output of MWEs, and the like) and provide formatted inline LaTeX and code snippets.
A similar question over on Stack Overflow mentions
StackPrinter, which also provides some sample Stack Exchange printable versions as a demo on Stack Overflow and Stack Overflow Meta. This is, however, not entirely integrated into Stack Exchange as far as I know. How about integrating it into the TeX.SX user interface?
Options I'm thinking of include adding that to the list of "actions" one can perform on questions/answers -
link edit print close flag. This would work well for questions or answers. But what about if you want to print an entire discussion (question and answers). Well, how about somewhere in the
Tagged / Asked / Viewed / Active part of the right sidebar? This answer also provides a nice view of a location for seeing a printer-friendly version of a post (question/answer):