[tzs]

This is not too rare when HN is being slow and giving those "We're having some trouble serving your request. Sorry!" pages.

If you get one of those on your comment submission you have no way to know if the trouble stopped it from accepting the comment or if it accepted the comment and ran into trouble then trying to display the updated thread.

For some reason I can't even begin to guess at HN does not seem to have protection against multiple submissions of the same form, so if after getting "We're having some trouble serving your request. Sorry!" on your comment submission you hit refresh again to display the page and the form gets resubmitted, you get a duplicate comment.

[saagarjha]

Earlier today when I was getting these I went to go check the page to see if the comment was posted there. More than once it said it failed but I was able to stop myself from trying again because it was actually there.