Revisions are not accessible
If I click the "modified [time] ago" link, it goes to the timeline instead of the revisions. The revisions can only be accessed by editing the URL ("timeline" → "revisions").
In this particular case, the edit didn't affect the visible text, so the diff doesn't show anything since it doesn't show the Markdown. (cf the revision with "side-by-side Markdown" enabled)
Update: All Post Timeline pages now have a link to Post Revisions (and vice-versa), so that's a decent workaround :)