bbp_mention_filter( $content = '' )

function bbp_mention_filter( $content = '' ) {

	// Get Usernames and bail if none exist
	$usernames = bbp_find_mentions( $content );
	if ( empty( $usernames ) )
		return $content;

	// Loop through usernames and link to profiles
	foreach ( (array) $usernames as $username ) {

		// Skip if username does not exist or user is not active
		$user = get_user_by( 'slug', $username );
		if ( empty( $user->ID ) || bbp_is_user_inactive( $user->ID ) )
			continue;

		// Replace name in content
		$content = preg_replace( '/(@' . $username . '\b)/', sprintf( '<a href="%1$s" rel="nofollow">@%2$s</a>', bbp_get_user_profile_url( $user->ID ), $username ), $content );
	}

	// Return modified content
	return $content;
}