The answer is - we both could be. There are no absolutes in writing. What works for one reader won't work for another. What one editor loves may be loathed by another. The requirements for one agent will differ from another (Carole Blake, for example, in From Pitch to Publication wants a lengthy synopsis and full character breakdowns, but most editors and agents in my experience want a brief synopsis, a page or 2 at the most). I was told by a friend that they'd had a positive response from an agent to their covering letter being actually a pussy cat card as they'd heard the agent was a cat lover. It's not something I'd advise - but it worked.
Use your common sense. Someone asked me recently about putting recommendations from friends and family into their covering letter, as had been advised by a tutor on a course they'd been to. I was horrified and gave the opposite advice. I reckon it's only common sense - of course your mum loves it, she loves you and unless she's the book buyer for Tesco her opinion doesn't mean anything except make you look amateurish. That seems commonsense to me.
Commonsense says that manuscripts should be easy and pleasant to read, so double spacing and one side of the paper only are good ideas. Ditto black ink on white paper: in fact, the 'rules' regarding format for manuscript presentation are all about commonsense. Is it easy to read? Then do it.
I write my novels in one long document and put it into chapters at the very last minute. I've got my reasons for doing this, and I think they're pretty good ones that I advise other writers to follow, but it might not work for you. If it helps, do it, if not, discard. Use your commonsense.
*(The correct answer here is me, of course.)
At last! I've got my finger out and have committed to running some day courses:
Writing a Novel - 31st July in Bath and 18th September in Truro
Getting a Novel Published - 1st August in Bath and 19th September in Truro
Contact me on firstname.lastname@example.org for more info...