Today I submitted an RFC (Request for Comment) as a Pull Request in wiki-client.
This particular hook would allow a plugin to parse the text of the paragraph and update the item structure or reformat the text before it's saved.
The broader idea is that there could be areas of core logic that plugins could extend by hooking in. This way experimental features could be tested out without updating the core.
It would also be a way for new core functionality to be developed in a plugin. That way wiki maintainers could disable or replace core functionality with different logic (for example, backlinks).
To test this functionality I created a Metadata 
plugin.
This way, I could add json to the story that other scripts or clients could consume.