Have signed on to one of these
I saw no ad, but I wasn't on for long, and this was a few months ago.
"...reassuring customers that they are using an official Comcast hotspot, "
Unnecessary, because you have to be a Comcast internet customer, and must use your Comcast username and password to sign on.
The nice thing about these hotspots is that once you sign on to one, they give you a cookie or log your MAC address or something, because you don't need to log on again if you go to a different hotspot. So, at least they did that part right.