A short example of how to enforce a maximum number of times a user can receive points for making a comment. Note that we count the number of times points have been awarded and not the amount of points user have received!

myCRED: Max. Comment Points

add_filter( 'mycred_add', 'mycred_absolute_limit_for_comments', 20, 3 );
function mycred_absolute_limit_for_comments( $reply, $request, $mycred ) {
	// Ignore declined instances or instances that are not comment related
	if ( $reply === false || $request['ref'] != 'approved_comment' ) return $reply;

	// The user ID
	$user_id = absint( $request['user_id'] );

	// Count the number of times this user has received points for comments.
	$total = mycred_count_ref_instances( 'approved_comment', $user_id );

	// Maximum number of times a user can get points for comments
	$max = 100;

	// We have not yet reched the max = approve
	if ( $total < $max ) return true;

	// All else we decline
	return false;
}