Dear Miss Snark,
Just when I think I feel confident about formating, a new question crops up. I just barely started my MA classes and the first thing my professor said was that we are to use ONLY ONE space after a period. His said that is what publishers want.
I so do not care about this. This is why professors should keep their pointy little noses out of actual, yanno, real work and stick to parsing out the motivation in Jane Eyre.
First of all, when you write a query, you're writing to me, an agent, not a publisher. Second, I don't give a flying fig about much other than spelling and grammar such that I have confidence you are the master of your art form.
When/if/should this great masterpiece garner an offer and acceptance for publication, then and only then will we begin to have fun with the style requirements.
And fyi, and fy professor's i, there is no such thing as "what publishers want". "Publishers" aren't a monolith. They EACH have their own requirements and what flies at Random House is sneeered at by ..well..others. And vice versa. They each want it done their own way and the only good thing about it is they tell you what they want, and acquisitions don't depend on it AT ALL.
Tell your professor to get back to editing his/her beloved literary magazine and terrorizing undergraduates. Leave the advice about publishing to people who actually work in the field.