Now I could be mean and ask for a donation or something. I know you are out there with the same problem I had. If you have found this site, like me, you have searched high and low and are desperate. In fact, I was just on a site that had a stuck welcome message, even mentioned it, cursed it, and had given up. So all I’m asking is that you come back every now and then and maybe leave a comment. I sincerely hope this helps you:
You can turn off the unwelcome welcome message in Settings-> Headspace -> Site Modules -> First Time Visitor. Uncheck the dumb little box.