Revert "Show comments by default"

This reverts commit fd8adbc6f5de9dc3274d448c4b35998a854a0159.
Revert "Introduce Disqus comments on posts"

This reverts commit 4f0552de6ff84ceb4f1ac75ffd2e1c516e036140.
Refer users to Twitter and/or email for comments

Because after two months, a couple dozen posts, and thousands of page
views, there were exactly zero comments via Disqus.