Eventually, somebody else at Renaissance Learning with more of a clue started responding to me, and suggested a factory reset. That didn't work, so she then said she thought there could be a problem with the control panel, and I should try reinstalling it, through Neo Manager.
I didn't already have Neo Manager, so I had to download the installation files from renaissance.com. Even though they're no longer supporting the Neo, the software and manuals are still available on the web page.
I installed and ran it, plugged the Neo into the computer, and installed Control Panel via the SmartApplets tab. Once it was done, I turned on the Neo, typed some stuff, and tried to delete it with the Delete key, and... it worked! No w's.
So here is the fix in case anyone else runs into this problem.