If you could unilaterally establish any rule at your startup/company...?

I would establish the rule that any unilaterally established rules should be ignored.

Require brevity in documentation, E-mails, policies, etc. Then employees think for themselves, ask questions, and avoid a lot of BS. :)

I'd make each instance of copypasta in code require board-level approval in writing. :)

No tabs, 2 space indent.