As I prefer using https I stumbled upon this bug.

When browsing the forum index clicking on any link the "last post" column will redirect you to the http version (although the link is displayed correctly in the status bar when hovering over it).

edit:
creating a post sends you to http as well. (I should post more often )

Not sure where or how to fix this one atm. I did a search for the obvious keywords (in the code and google), but haven't found anything relevant so far.