I can’t remember where this was said to me, but I think someone (maybe nightpool?) suggested that Note could be used for message passing a la Discord, which would be a third distinction and perhaps better than length/newlines or plaintext (as explained previously why those are inconsistent). So in that case, we could say Note vs. Article is one of formality. IMO this could complement the Article-to-<article> suggestion above.
Taken together:
- Note = for informal message-passing
- Article = for publication or syndication
The only thing unresolved with this distinction would be the blurry line that is microblogging. Microblogs are often both informal and intended for republishing in feeds. It’d be pretty clear-cut to use Note for a messaging application and Article for a blogging platform, but… perhaps this implies top-level microblogging posts should be an Article and replies should be Note? Or that they should all be Article regardless of the fact that they are informal? There’s still room for discussion there.