When you enter the MMO-C forums from, say a Google link, and this link includes mode=threaded in the GET headers, the view mode will permanently changed to "threaded" until you update your General Settings page... Where it'll still be set to whatever mode it was set to to begin with.
As a programmer I didn't have much of an issue figuring out what was going wrong (cookie mmo_threadedmode=threaded is set despite user being logged in/mode is not checked against user settings), but I reckon that a regular user would have a harder time figuring out what was going on
And I personally appreciate that But yea figured I'd warn others because it took me a sec to realized why my view had randomly changed on other pages too.