Fair comparison
Universal Document vs Markdown
Markdown is lightweight authoring text. UD is designed for richer structured state, metadata, revision relationships and evidence.
Not a forced replacement
UD is designed to coexist with established formats. The practical question is which object should carry structure, state and lineage, and which formats should remain compatibility exports or required delivery formats.
Evaluate with one real workflow
Compare how each approach handles revision, finality, portability, machine readability, provenance and recipient friction.