Comment by dang

Do you mean what gets re-upped directly vs. what gets an emailed invitation to repost? It's a purely technical distinction based on how many stories we keep in RAM (currently a few days' worth). When a story is older than that, it's a pain to re-up it, so we started emailing invites instead. I spent some time working on the code to eliminate the distinction, but actually I think this may be one of those cases where what seems like an arbitrary restriction turns out to have more value than that. There's something about the "working set" of stories over the last few days that's different from the longer-term history of the site. Right now the system treats the former as mutable and the latter as immutable; you can think of the invited reposts as append-only rather than writeable. That somehow feels right to me.