I just posted a new topic to the "How to and troubleshooting" forum here on WordPress.org
Then I went to post a follow-up (I managed to resolve the problem and wanted to update the topic).
But when I tried to post a reply it said "This topic is closed".
The URL of the topic is http://wordpress.org/support/topic/header-error-generated-via-link-templatephp?replies=0
I can view it when I'm logged in, but can't view it if I'm logged out.
Is this because topics need to be moderated first, before they appear on the site? (If so, there should be a message to alert the user to that).
If not, then why was my topic closed a couple of minutes after posting it? Weird.