The author lost me at the last bit where they started using weird names for the posts. Why would you make one ID O and the other ID 0? Why single letters and not EMBED_01? Why seemingly random letters instead of ABCDEF? Does OCPDST stand for something?
They are placeholders, their meanings are spelled out in the post:
That doesn't actually answer any of my questions though. Why is `S` the placeholder for "post"? T for T'outer?