Some were starting directly from level 2. I thought I had fixed those,
but it seems I had only looked for '----' styled headers, not '##'.

command ran: find -name '*.mdwn' | xargs sed -i 's/\[\[\([^|]*\)|\(http[^]]*\)]]/[\1](\2)/g'

Former-commit-id: 110a316cc43754209ad4e3c788ef348654f3567a

Former-commit-id: dcad2171d5900cb5ddf9b6b869e5ee758af7f6f7