So it looks like #Jekyll doesn't have a standard way of storing comments. OK, fair enough, it's not like static HTML can accept comments.
But I don't need to set up Disqus or Github issues or anything like that just to display *existing* comments on an old blog that I'm converting. And I don't want to just paste the comments into each post.
I'm looking at this approach, minus the handler for new comments. Looks like it might be the best fit for the use case.