Make updated principles more robust

As a follow-up from !4011 (comment 2115414137):

How might we add a line or two to each principle's description about the downsides we see with being “opaque” or “task-driven”? In those descriptions we talk about what we want to encourage, but we don't contrast that enough with the behavior we do not want to encourage.

How can we add more concrete examples of behaviors to make the dos/don'ts section clearer? See this comment.