My commute home was spent fixing the display of "related posts" in the comments. It's supposed to show the post title but I still had a number of posts from last year that had none - from before I started automatically replacing them with the date/time.
Even after adding the date/time to those there were still instances of related posts being listed with no page title. I couldn't figure out why until I realised they were from before I changed the permalink structure - the redirects were preventing the page source being loaded via curl.
I, therefore, had to reuse the code snippet from my 404 page to grab the new, redirected URL. Problem solved!