Why is one not able to tweet "Get Better"?
Is one not able to tweet "Get Better." because it's something Dorsey's father used to say?

The reason that certain tweet content appears to do nothing is that Twitter is interpreting them as commands, according to this article:


  
  GET [username] - retrieves the latest Twitter update posted by that person. You can also use g [username] to get a user's latest Tweet. Examples: get goldman or g goldman. 
  


—Twitter SMS Commands

The get command will send the latest tweet from the named user to your phone. I've tried some of the other commands listed in that article, and they don't post a tweet. They do, however, have the listed effect. For example, fav accountname does indeed mark the most recent tweet from accountname as a favourite.

It's perhaps useful to remember that d accountname Some message here will send a direct message to accountname, even if entered in the public tweet box or via another client. This shows that they have a standard text to action parser that works on tweets as they are submitted.

So, to answer your question: No, it's not down to Jack Dorsey's father. It's purely because Twitter is interpreting it as a command. Sorry!
    