More tweaks to surprise and end section

- Remove failed attempt to use "ignorance" literally and replace with
  wording from principles.txt
- Clarify that seciton about "surprise" applies regardless of _intent_,
  since it's about how the recipient is likely to feel.
- Add stronger wording reminding people that the EC is never the wrong
  answer: While we want to encourage "grown up" communication, it should
  not be the case that people feel they can't be in SIPB if they can't
  confront people about their behavior.  This should result on a balance
  on the spectrum between "tattling" and people feeling fully empowered to
  challenge others on their violations of these principles.