Duplicate comment detected on failed posts

[frenz0rz]

So it goes like this. You read an article, and want to post a comment. You spend 15-20 minutes writing a nice, lengthy, well deliberated response, and click to send it. The page reloads and you're brought back to the comments thread, but your post is missing. Assuming its probably a technical fault, you wait half an hour or so before returning. Nope, your post still hasnt appeared. Thankfully you had the foresight to save your post (or use a handy browser add-on (https://addons.mozilla.org/en-US/firefox/addon/lazarus-form-recovery/) to remember it) and you try to send it again.

"Duplicate comment detected; it looks as though you’ve already said that!"

The result - that comment is now essentially unpostable.

I've experienced this occasionally but have noticed it becoming slightly more frequent as of late, and have lost a number of comments as a consequence. Does this happen often to anyone else?

[CMaster]

If your post doesn't appear, it almost always means it has been flagged as spam.
It may or may not get rescued at a later date.

[frenz0rz]

If your post doesn't appear, it almost always means it has been flagged as spam.
It may or may not get rescued at a later date.

I see. And do you know the criteria for this spam detection so that I might avoid it in future?

[TailSwallower]

I'm almost certain that posting multiple links gets it automatically flagged (even if the links are all relevant and/or interesting) but other than that I'm not sure.

Obviously it's also the sort of thing that the mods may not want to share - knowing the exact triggers could make it easier for the spammers in the future.