Tim Nahumck, writing about the latest Drafts update for iOS:
One thing that is included with MultiMarkdown as an option is Critic Markup. Looking through the guide, there are several helpful elements that can be used for editing my writing utilizing Critic Markup. I can highlight some substitutions, additions, and deletions. I can highlight text to show something I might want to work on later. I can also add a basic comment somewhere that won’t be shown in a preview. And with this action, I can easily add any of them with a tap and a text entry, which inserts it in the proper format. This is helpful for creating and previewing the documents in Drafts, and gives users the flexibility to mark up files and save them back to a cloud service. I can see myself using this a lot for longer posts or large reviews. I’ve even modified my own site preview action to render the MultiMarkdown via scripting, as well as updating both my standard and linked post WordPress publishing actions to do the same.
I've always been a fan of CriticMarkup but have never been able to get into it as it wasn't integrated with the text editors I used on iOS. Considering how Drafts is my favorite option when it comes to writing and editing certain annual long-form stories, and given how I came up with my own syntax in previous years to embed comments in Markdown documents, I'm going to give this a try.