It's the default on most if not all major wikis.
There hasn't been a lot of response on the request but so far all positive.
http://www.mediawiki.org/wiki/Project:Requests/RfC/Allow_blocked_users_to_edit_talk_pages
Version: unspecified
Severity: enhancement
URL: http://www.mediawiki.org/wiki/Project:Requests/RfC/Allow_blocked_users_to_edit_talk_pages