Yeah, that's gonna get pretty annoying : ) That "global sync" option is only for that one slide deck though (for demo purposes). If you upload your own deck, only the uploaded gets to control the slides.
There should be a different demo page for each visitor. I was confused and thought it wasn't working well at first.
Regular presentation are only controlled by the author. I made a special case for the demo. Yes, there should be a unique-sync code for each visitor to the demo. I though the universal sync would be collaborative. Might have been my mistake.
I wouldn't change it. When it is going crazy it only reinforces the power of the Sync tech you are doing.
Good advice. The happy medium is a unique code for each person who click the demo link. Firebase would make this easy. Thoughts?