I fear that what I wrote wasn't clear. The rule about significant attention only applies to stories that are less than a year old. After a year or so, reposts are typically ok.
Aren't submissions folded to the last one, if the URL is the same?
I could swear I have seen that even when the prior submission was a few years old.
Does the algorithm to decide that take comment activity into account?
The algorithm doesn't currently take the time of submission or number of comments into account, but we're working on a new implementation that will handle all of this.