Force Profile link for username, and stop “Website” field on Profile from becoming offsite link atop Comments, in “Recent Comments” list, etc

Yup, there’ll be no link when the user doesn’t fill in that field or when leaving a comment as a guest.

As far as redirecting comment links to the bbPress profile goes, popping this in your functions.php should do the trick:

/**
* Redirect user links in comments to BBPress profile
*
* @param object $comment 
* @return object
*/
function wpse425792_comment_author_url($comment) {
    if ( $comment->user_id && function_exists( 'is_bbpress' ) ) {        
        $comment->comment_author_url = bbp_get_user_profile_url( $comment->user_id );
    }
    return $comment;
}

add_filter('get_comment', 'wpse425792_comment_author_url');

[Edited to add a missing “)” on the “if” line. This note added to get around the “Edits must be 6 characters” problem.]