I didn't see it on YC, nor did I see it at MS. I saw it on Flowing Data. I found it thru them, thus I posted it thru them. If they get left out perhaps they aren't needed thus we all have to do more legwork to find interesting things. JMHO.
But HN guideline[1] suggests that please submit original source.
Please submit the original source.
If a post reports on something found on another site, submit the latter.
That being said, I missed the trending last week, so I was happy to see it :)
These rules maximize the overall quality of the site. It's certainly true that not everybody sees every post; but if we went with that logic, there would be no such thing as a duplicate at all. That would be bad. Front page space is the scarcest resource on HN, and needs to be distributed across as many high-quality stories as possible.
A great tool for running across interesting stories that you didn't see on HN the first time round is the 'past' link in the top bar, which lets you browse HN's top stories day by day.