This comes up about once a year. The previous ones with many comments, including further context, are https://news.ycombinator.com/item?id=1282213 and https://news.ycombinator.com/item?id=6426605 .
I'm intrigued. Today you have found two dupe posts coming from me.
How can you be so fast finding the dupes and replying with this info?
It has to be a very time consuming task if it is not automated (appreciated anyway).
If you have automated the task I want to know how! :-) (If you could briefly explain)
In both cases I've just posted it and expected to upvote the most recent thread, but a new post was created and I have directly supposed that the stories were new (from the forum perspective).
I don't understand the mechanics by which the forum allows dupe posts. Maybe it should only allow to dupe a previous post when it's very recent (less than a day) and don't have any upvotes, or automatically show the previous discussions when is old (months)
I recognized the posts. The packing one was only last week, and this DNS Legend one, while older, was written by someone I know.
When that happens, I go to the search link at the bottom of HN, and look for the title, or use the key words. That finds the hits. I then check to see if there were many comments.
The FAQ says "If a story has had significant attention in the last year or so, we kill reposts as duplicates. If not, a small number of reposts is ok."
Duplicate posts are hard to detect. The packing one from last week has a tracer on it, as "?src=hn", so the URL is different than the one you submitted. Also, due to the vagaries of voting, sometimes the moderators think a post didn't get the notice it should have, and don't weed out duplicates even if there haven't (yet) been any comments. There's also a problem if a dozen sources report the same topic, like when Citizenfour recently won the Academy Award.