Hi Gerry, I stumbled upon your post mentioning tree-sitter. Now I just found your tree-sitter repo.
We at org-parser have a pretty much complete EBNF grammar of the org syntax. Maybe it can be converted with some tool and kept in sync for the tree-sitter grammar? I don't know anything about the grammar required by tree-sitter, but maybe these projects can work together?
The raw parse tree from org-parser will be transformed to a simpler AST, but for tree-sitter it might already be sufficient. Although, not all styled (esp. nested styled) text in org-mode is recognized by our parser because it's hard or impossible with only EBNF.