What functionality is missing? What is unsatisfying with the current situation?

  When posting in the session stream as a GM, all players can see the post. The ability to specify which players would be able to see the posts in the session stream could add more functionality.   With the current setup, only general messages can be put in the session stream. If you want to share written secrets to a single player you are forced to do a workaround of using a notebook/article with subscriber groups to share secrets during a session. For me, a lot of this type of information arises on the fly and is improvised. It can be cumbersom to have to write out a note, configure the subscriber group, and then wait for the player to be able to see said note, all for what is usually only a few lines of text.  

How does this feature request address the current situation?

  Adding a way to ~Whisper~ messages to players adds more utility to the session stream in a way that parallels many of the major online tabletop rpg systems. On top of adding a highly used feature from other systems, this feature prevents the need of the cumbersom workaround of needing to create articles/notebooks with subscriber groups whenever secret information needs to be divulged to select players on the fly.  

What are other uses for this feature request?

  Although I am only proposing the ability for the GM to be able to post messages only select players can see, this could be extended further to allow for players to post messages the GM cannot see. Useful for strategic planning in moments where you want to get the upperhand on the GM's monsters. Perhaps this may open the door for being able to privatley roll dice as well.