Can't return to a comment -- Comments posted after a logout disappear

I was logged into drupal.org and writing a comment.
While I was writing, something had happened with my login -- other drupal.org pages in other browser tabs showed me as logged out. I assume my login cookie had expired. I logged back in in one of these windows.
I posted my comment in the original browser tab. I got a 'You don't have the rights to post here' message -- I was logged out in this tab.

I hit back in my browser to repost -- but the text I had written was gone.