While it’s never really caught on with any of the larger publishers, CriticMarkup is a great tool when working on edits between collaborators using Markdown or other plain text formats. It lets you specify insertions, deletions, substitutions, and comments, all with the option to include attributions, timestamps, and other notes.

The syntax isn’t fast to type, though, and additional tools are needed to handle viewing it in any intuitive way. The CriticMarkup Toolkit offers a lot of integrations, but my favorite thus far has been the way that Fletcher Penney has built it into MultiMarkdown Composer.

As a side note, while MultiMarkdown Composer offers a CriticMarkup preview, I tend to use Marked 2. I’ve added quite a few CriticMarkup features to it, including the ability to automatically detect CriticMarkup syntax, process it for preview, and display a menu for switching between markup, edited, and original views. You can even set Marked as the default preview in MultiMarkdown Composer Preferences->Preview.

The first major feature in MultiMarkdown Composer of note is the Track Changes feature under the View menu. With this turned on, it will add the syntax for CriticMarkup automatically as you make changes. For example, if you delete some text it will surround it with {--deleted text--} instead of removing it, and it does a great job of deciding how to handle changes versus insertions. You can also define a default comment for changes in Preferences->CriticMarkup, so your changes can automatically be tagged (e.g. with your initials and a timestamp). This makes it easier for multiple people to offer input and have changes attributed.

Under View->CriticMarkup Preview, you can use Original Version or Changed Version to revert or accept all the changes in the document after reviewing. You can also see a panel with all of the changes in the document using Window->Show Change Panel (or using ⌘⇧V). This panel allows you to click a change to jump to and highlight it in the document, then click Accept or Reject in the panel to deal with each individual change.

Lastly, a feature I love despite that fact that I only need it on rare occasions: file comparison. You can take any open file and use File->Compare to Other File (⌘D) to create a new buffer containing a “diff” style comparison using CriticMarkup syntax. This makes it possible for someone who isn’t familiar with CriticMarkup to send you a revised file, and then easily see and handle the changes they made.

Another side note, if you want change tracking combined with version handling, Draft Control is a very capable and interesting option. Not so much for collaboration, but for your own work it’s pretty handy, and also works with Word, Pages, LibreOffice, Scrivener, LaTeX, PDF, and quite a few other filetypes.

All of these tools combined make it even easier to avoid using Word or Pages. For this and many other reasons (autocomplete link reference titles, easy footnotes, document navigation, and more), I highly recommend MultiMarkdown Composer as a primary Markdown editor on your Mac.