I usually leave cookies turned off at home (and on at work), so I was surprised to see some differentiation in the thread folders tonight. While I’ve checked, and, sure enough, got’em turned off, the thread folders are differentiated by color and down arrows as to whether I’ve viewed 'em. How’s that work?
“Turning off” the cookies just turns off your automatic login.
You still have the last login info part of the cookie.
To really get rid of the cookie, like if you don’t want the tech guy at work to bust you, search for a file like “. . .@boards.straightdope[1].txt” and delete them.