You absolutely have to split jade documents and use includes/blocks though, any decent sized page, even if it's static becomes unmanageable very quickly.
Certain elements are, or can be made to be, "inline" which gets them treated the same as characters on a line. Thus those elements, such as an image, will have white space between them as a word does in a paragraph. If you butt those element's tags right next to each other, with no white space between them, then there will be no white space on the displayed page.
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