I was wondering, have you considered switching from pulldown-cmark to markdown-rs? The former hasn’t been updated in a while and has some nasty limitations, e.g., missing footnotes.
markdown-rs seems to be feature complete, actively maintained, fast, and correct, so maybe it is worth switching to?
I think going to an AST like markdown-rs is going to make it difficult to implement features, we can’t hook in the rendering like we’re doing now and we won’t be able to change the AST since it’s going to be limited by what’s in the library (eg adding classes/ids to a heading)