The table syntax extension in the top comment is interesting — it solves the readability problem without breaking unrendered markdown. The ::y1 approach degrades gracefully. One thing I keep running into with these markdown supersets: the rendering gap. You write locally, push somewhere, and suddenly the :::columns block is just raw text. Marp handles this well because the VSCode plugin closes that loop immediately. Curious how MDV handles the renderer portability problem — is the spec open enough that editors could pick it up, or does it depend on the MDV CLI being in the chain?