blog: rewrite "Played in the open" — grounded, casual, public-by-default fixed (#139)

Three real problems in the first draft, fixed:
- Framing bug: it said "three separate yeses have to line up before a clip shows,"
  which made the public-by-default thing sound like an opt-in lock. Corrected to the
  truth — clips go up public by default, you consented at upload (no extra step), and
  there are two OFF-switches (you hide them, we can pull one). …