Having this functionality also track parser functions/tags that aren't actually supported (and thus are just output as plaintext by the parser) would aid in day-to-day wiki maintenance. If this can be and is added, it would probably be a natural fit for Linter.
Topic on Talk:Requests for comment/Parser function and tag tracking
I think this makes sense for Linter, in the sense that unrecognized tags are an error, but I would not want to implement this as part of this RfC, which is just limited to parser functions and tags that exist.