I think im looking for the same:
I have on the acount page double blocks and want to remove some from the left sidebar.
But in the <customer_account_index> XML there is no <reference name="left">
so I think you have to add that and then somehow remove the blocks which you dont want in there.
like there is My Orders block there i’d like to remove but dont know how, anyone?
I have added this but it doesnt work :(