Since yesterday evening our comments feed has been feeding only comments from 18 April. Other Blogspot users including NZ Conservative have reported the same problem so it looks like it's Blogger's error rather than ours, but I notice Fundy Post's and Hand Mirror's feeds are both fine. Most annoying. I've turned Recent Comments off until Blogger gets it sorted.
Updated 1pm: Thanks to David for advice on how to fix it - all working again now.