(cookieless again)There's a thought, Dave B!
Actually I use a Mac, and FWIW, I never had my cookie "reappear" magically on any computer except that one time (at least as far as I can remember).
I can MAKE it go away--e.g., if someone else wants to visit the Forum using my computer-- when I'm using Explorer, by going to "Preferences" and then "Cookies" and deleting the cookie--or by logging out. (The former is quicker.)
But whether the cookies disappear when I disconnect from the internet seems to depend on whether I go to Mudcat via AOL, Explorer, or Netscape, among other things.