Um... Bulbagarden has its own Training Center. You most likely didn't see 'cause it has been a long time since someone posted there and thus it became hidden to you by default. (Threads with no activity for one month becomes hidden to the user by default and can only be found again if you change the setting such that you see all the threads from the beginning)
On your bank post, click the "Edit Post" button and then the "Go Advanced" button. On the next page that you see, look for the checkbox with the "Show Your Signature" text next to it and uncheck it and save your changes. =)