I'm an idiot, I guess. I actually understood all along. I recognised that the initial score for new submissions would be monotonically increasing, but the graph's x axis was throwing me, by making it seem as though a single story over time had its score dropping, but that's not it. If it were flipped horizontally, I think that would be more intuitive, maybe, since it might capture "these later (further-to-the-right) bars are newer stories" instead of stepping back. Or maybe not, and I'm just an idiot. :)