A comment is a hm://z6MkfzKMhF9k1oPaQsShWAg8xJzbWf5kaZgn1MkeZvhcAsmB/concepts/resource/snapshotresource that describes content from a single author.

All comments in our current system require a target Document, where the comment will appear. A comment can have a parent comment, when the author is replying to another comment.