When trying to post an update to a thread, I got the following

To create a new thread in Number crunching you must have a certain level of average credit. This is to protect against abuse of the system.

On playing a little, I discovered I had somehow been logged in with an email I have not used for well over 15 years.

Edit:This happened from clicking on the short cut from the home page on Firefox that normally logs me in automagically with my current email and account.