Under Tools->Edit Options, all the way at the bottom there is a setting "Message Editor Interface". It was defaulted to "Basic Editor - A Simple Textbox" for all of the users brought over from the phpBB boards.
I think for usability sake, it should have defaulted to "Standard Editor", so I just updated the setting for everyone who was set to "Basic", moving it up to Standard.
This was a one-time change.
If you really prefer Basic, you can go into your options and set it back.