Automatically Post on Facebook user wall after Comment

You can't. There is an option in the comment box for the *user* to choose if they want the comment to go to their Facebook wall. You, as the admin, can't force every comment a user makes to go to their wall.

I hope that helps explain,
Alex

There's no way to control the default of that box. Facebook has complete control over it. We have seen sites where it enabled by default. The only explanation we've heard is that Facebook looks at the history of all users that have posted on the site to determine if most want the comment pushed to their timeline and, if so, will enable the box by default. Additionally, if the user has previously commented to the article or site, that can be used to influence if the box is enabled.

Again though, there's nothing we can do to influence the setting. If so, everyone would make it defaulted to 'on', of course, because everyone wants their content to go to user's timelines.

Thanks,
Alex