What does the "Custom Description" do?


I'm trying to add some end-user visible documentation for a database reader node that I'm pre-configuring. I tried adding my text to the "Custom description" box in the "Edit node name and description" dialog, but this doesn't do what I expect (i.e. replace the contents of the Node Description pane).

What is that Custom description box for and what should I do in order to provide docs to my end users?