Here's what I mean:  Launch New Sonar (with or without C3 - doesn't matter), go to Help, About Sonar, and under "Account Name", it's blank... at least it is for me.
 
I'm guessing it's supposed to display your CW user name - as it does in the C3 window.  
 
Despite showing me as a non-person, the program is fully functional (not demo) so my feelings aren't all that hurt.
 
So, is it blank for everyone, or just me?  (I'm running Platinum BTW).

Same here.
 

Yes I have noticed this too. I hope they fix it. 

Run Regedit, and navigate to:
 
HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\Platinum
 
And enter your full name in the User Name value.
 
This will also be used for the Author and Copyright fields in Project Info, so you probably don't want your forum user name there.
 
On my desktop install this registry value and Project Info said "brundlefly", and on my laptop they were blank.