As you make allocations you can simultaneously write a detailed log entry about the changes for others to see. These notes can be seen in the Project's Dashboard under Resourcing Log.

As you start allocating in the grid view a field for adding a comment also activates: you can type a comment in this field regarding the allocations and save that and the resourcing changes by clicking Save Changes.

In the project's actions you can find the Resourcing Log ... button:

This view combines all the log entries made for your project: