Oh good, now I have another 4,000 word blog post draft that I'll probably sit on for a while because I don't know how to edit it into something coherent 😓

(This one's all the technical details I've learned about how RSS/Atom feed publishers can implement RFCs 5005 and 6721. It's not going to be exciting to all that many people. I just hope people who develop blog/CMS software find it helpful...)