Can confirm discourse.codinghorror.com is no longer sending a HSTS header at all:
$ wget -O /dev/null -S https://discourse.codinghorror.com -q
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 13 Jul 2017 22:04:15 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Accept-Encoding
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-Discourse-Route: list/latest
Cache-Control: no-store, must-revalidate, no-cache, private
X-Discourse-Cached: true
X-Request-Id: f40d4ea9-375a-4a9e-b6e1-c7500ffa194f
X-Runtime: 0.002585
X-Discourse-TrackView: 1
Referrer-Policy: no-referrer-when-downgrade