The memo key is only used by witnesses to be able to read the data we send in the blockchain so they can built the price feed and adjust some parameter. You wouldn't need it to burn shares if you decided to.

Yeah, but for a theoretical MPA - if we were able to read the memo of a burn/null account then you could destroy some of the MPA to change an algorithm based asset's variables. Say destroying a few thousand $ of the MPA to increase/decrease the appreciation/depreciation.