The Sales Partners Commission report under Selling is a nice fetaure especially for marketplace sales. However, it is fundamentally lacks the time dimension and does not take into account the returns in Sales Invoices.
Simply put, the positivity constraints on the base_net_total and thus total_commission is producing only forward sales process.
AND IFNULL(base_net_total, 0) > 0 AND IFNULL(total_commission, 0) > 0