I must say Ruhoh API is very well thought out. Kudos for the great work!

How about extending the Universal Blog API for storing user comments? That'd make it a complete out-of-the-box blogging solution (a user may opt for using a comments service provider like Disqus OR use the inbuilt comments API). The spec could look somewhat like so:

- Directory Structure:

          _comments //folder with json files containing user comments

- Comments file:

          {{post identifier}}.json //could be simply the post filename.

- Comments structure:

       {
           "comments" : [{
                         "id" : "1123",  //unique comment id
                         "author" : "Chuck Norris",
                         "author_handle" : "chuck@norris.com", //or a website
                         "date" : "yyyy-mm-dd", //comment date
                         "content" : "Hei! Chuck makes dumb comments."
                         },

                        {
                         "id" : "1124",
                         "author" : "Superman",
                         "author_handle" : "superman.com",
                         "date" : "yyyy-mm-dd", 
                         "content" : "Superman is scared of Chuck."
                         },
               ]
       }

We can leave the comment id and author details up to the login implementation.