If the admin bans a user, should the username still appear in the memberlist? And if the username is banned and deleted, can the user register with the same username again (from another IP, if the IP was banned too)?
The username should still appear in the memberlist. It will, unless you delete the user entirely. If you do delete the user then yes, they can reregister with the same username.
at www.spamdiet.com you can update the phpbb software banlist if you got alot of spam. they got a huge global banlist with spammers
Please search at PHPBB forums , i found a modification for same, or i will dig out the link for you soon !