• WP:BLP: "Posts left by readers are never acceptable as sources"
• WP:NOR: "A and B, therefore, C" is acceptable only if a reliable source has published the same argument"
• WP:NOR: "It is not acceptable for an editor to use photo manipulation to distort the facts ..."
• WP:CIV: "Personal attacks are not acceptable anywhere, but ..."
• WP:NOT: "User pages that move beyond broad expressions of sexual orientation are unacceptable"

Imperative command. E.g.

• WP:V: "Do not leave unsourced or poorly sourced material in an article if it might damage the reputation of living people"
• WP:V "Even when information is cited to reliable sources, you must present it with a neutral point of view (NPOV)"