I think this a feature of accounting practices. Mark down rent means you mark down the asset value of the building on your balance sheet. This reduces the value

I think this a feature of accounting practices. Mark down rent means you mark down the asset value of the building on your balance sheet. This reduces the value of your business which means loans secured against the business are in jeopardy and it limits the potential to borrow more money. This is why commercial rents going down is a rare event. Fwiw i am not an accountant and could well be wrong.