This is more of a Shawn / technical question that probably only he could answer: but why use the Stack Overflow method of user lands on page, detect cookie, AJAX login and refresh to have a logged in session? Just a technical mind curious to this choice...
Oh... I think that's how XenForo does the Facebook auto-login since it has to make a call to Facebook and then you get redirected back real quick. So I guess that's a good reason to do a redirect login (it's not AJAX though).
Well, shit. I didn't even realize I was being logged in via Facebook. :/ I've never noticed that via anywhere else, but then again, I may not have linked Facebook log-in there.
You could test it... but I'm 99.99% certain that's what it is. Log out here, and log out of Facebook and I suspect you won't see it. If you want to just stay logged in with your normal credentials, just log out and then back in with the remember me option. I think the Facebook log in only kicks in when you aren't logged in with your normal username/password.
I think also that whenever you come here, the plugin (or whatever it is) just checks your Facebook account (if you signed up with Facebook), then automatically you sign in. I mean, as a user who connects here via Facebook, it is something practical for me that i don't need to click on the "connect with Facebook" button and it just automatically signs me in.
Yup, that was it. I guess I never actually had a facebook connect login on XF to notice this elsewhere. Yup, I agree, I just didn't realize it was Facebook logging in versus XF logging in. Its been a long week or two.