At the moment automatically generated URLs inside a post (as in URLs that are not generated with the [URL] bbcode) are using an hardcoded template instead of the standard bbcode.html template (in case of prosilver). For prosilver this means that a link generated with

http://www.google.com

looks different than one generated with

[URL]http://www.google.com[/URL]

as bbcode.html adds a class to the link.