This is the third time someone has asked me this since yesterday, so there's clearly a real question here, and maybe a solution that we haven't found yet.

We can help 'propel' things for a few hours, but after that the posts look weird on the front page, e.g. if they have say 3 points and are many hours old. Plus we want to be able to invite reposts for things that are much older. If we notice—or anyone points out—a years-old submission that was fabulous and went nowhere, let's give it another shot. That's not an uncommon case.

If anyone can suggest a better solution than "make a new post in append-only fashion" I'd love to hear it.