In accounting, are you not counting expenses twice when you use LCM? First when you take a loss when reducing the Inventory value (since NRV is derived from Sales Price less Expenses) and then when you actually record the expense, like Commission Expense for example?

By LCM I'm assuming you mean the lowest cost to value the inventory. If the replacement value of the inventory is lower than its actual cost then the excess costs incurred are a charge against the revenue of the period when the costs were incurrred. Once the adjustment to the value of inventorty has been made the margin will be calculated using that value. You have to be aware that a lower may also mean a lower selling price. I don't understand the reference to commission since this is a separate item which is not part of the cost of inventory. In a double entry system it is not possible to duplicate transactions without a deliberate error since a transaction should be unique within the system