DoublePost

A double post is a post whose primary link has already been posted before in the past. You shouldn't do this.

"This post was deleted for the following reason: actually, no matter how much the site rocks, double posts after only a year really aren't okay." - jessamyn

Avoiding double-posts.

You can avoid double posting by reading these [suggestions]. Generally:

• Some people think one year should be the statute of limitations for an identical link. Posts with identical links within the last few years should generally be avoided and are sometimes removed if they haven't changed significantly since they were last linked.
• Posting a topic that covers similar ground to an FPP already on the front page may be flagged as a double post and the original poster told to post his or her links in the already open thread.
• Identical content at a different URL may also be called out as a double post. Be sure to search for keywords as well as URLs before you post.

While the best practice is to avoid double-posts as much as possible, it's also advisable to flesh out a double-post with supporting links, if you want to justify a new thread. See WhatIsAGoodPost. Canonically Good Posts are less likely to be criticized, ignored, or deleted.

Candidates for double-posts.

Flash games. Oddball news items (this broomstick, it vibrates?).

Exceptions.

A link in a comment may be "promoted" to a front page link, especially if it marks a new branch of discussion. A same-topic link is probably a poor candidate. There is a lot of debate about the proper way to deal with UpdateFilter? topics.

Calling out double-posts.

Usually someone will notice, probably a longtime regular. There are a couple of acceptable ways to do this.

• A terse note where the wording links back to the prior thread.
  • "Already discussed."
  • "Prior discussion of ______."
  • "Crosslink to earlier thread."
  • "Seems strangely familiar."
• A general comment as above, leading into on-topic discussion.
• Noting the double, but adding supporting links.

Because MetaFilter is SelfPolicing, this is not rude -- though it may feel intimidating to new members. Nor is it necessarily criticism, beyond a reminder that the poster might need to use the search function more. If the time period since the original thread is sufficient, it is probably just a reminder for other readers, and an invitation to check out the discussion there.

Unless someone has just reposted the vibrating broomstick for the 17th time, direct rudeness is unlikely. If you're calling out such a double-post, be kind. In egregious cases, your double-post will be treated as a DeadThread and fill up with injokes.

If your double-post was especially recent, though, someone will usually point that out. Take that advice to heart. Use Search better (keywords as well as URLs); keep track of [InJokes] which frequently point to DeletedThreads; and use your judgement.