For example, checking downforeveryoneorjustme.com or asking if a co-worker can reach a web site is different from contacting the site's operators to tell them about the trouble you're having.
I attempted an analogous investigation before posting. I tried Private Browsing mode, which worked. I tried different browsers, which didn't. The next step in my investigation before emailing YC/PG was to find out if it was just me on this local network, and the only way I had to investigate that was to ask someone else. The only way I could do that was to post to HN. It seemed the obvious next investigatory stage.
"I wasn't asking for support, or reporting a problem to HN, just seeing if it was a local SNAFU."
I asked how submitting a story to report a problem was different than submitting a story to see if it was a local SNAFU. And you brought up isup.me which would have been useless since the issue was related to logins?