I have my document open in SketchUp 2016, having just downloaded it from my.sketchup. The “SketchUp BETA || my.sketchup.com” logo is still present in the top-right corner.
Isn’t that logo a sketchup style? I haven’t investigated if it is as I assumed it was. If you save a sketchup file with a given sketchup style it saves the logo. Watch for watermark settings on your sketchup styles manager and I bet you find the logo there.
I just made a file in My.SketchUp, saved it and then opened it in SU2016.
I was expecting it would be a style thing as suggested by JQL but I don’t see a unique style nor is there a watermark.
So it is - changing it to an inbuilt style removed the logo. Cheers!