I was reading this thread and the important concept of finding the original source came up. I think two things that a lot of content aggregators run into as they grow is people will often post links from low-quality sources, and when a big newsworthy event happens a lot of similar links from multiple sources appear at once. Obviously not a big problem here now, but it may happen as Tildes grows.
Both of these issues often require significant moderator input, either through deletion of duplicates or banning of unsavory sources. One way we could instead approach this issue could be to allow for "alternate sources" to a story. For example, if a user is unsatisfied with a link to a news article, they could submit an alternate source to the thread that would show up in the discussion. If enough other users prefer that source, it could replace the link in the OP. The original source would still be visible, but all alternate links themselves could be ranked within the thread.
It seems the primary focus of Tildes is to be a discussion board, and so in my mind that means the link that engages the discussion doesn't matter much -- if we are voting on individual links anyway, this could be a way to automatically compile multiple similar threads into a single discussion.