If it doesn't specifically say in the instructions to use MLA format; or double spaced; or anything similar........ then stick with single space. It shows you aren't trying to "Dance around" the requirements. Not Good.
On the other hand, if it SPECIFICALLY SAYS to format a certain way; and you don't; then that shows you can't follow instructions. Also not good.
If you still think there is some ambiguity in the instructions, then there's no penalty for calling the MOC's office and speak to the staff member handling nominations and ask them to clarify.