Why should banned users be allowed access to any features of the site from which they are banned? Makes no sense. When I toss someone and shut them out of a nightclub for being assholes I don't let them in at all for a period, why should I? "I swear, I'm only gonna talk to the bartender and I won't drink!"
Banned is banned, if someone does something stupid they should be punished for it. I can't say I agree with all the bans in here (or the lack of them in some cases) but the rules on banned users are as they should be imo.