I missed one setting in the StopTheMadness extension and it seems to work now. Just like you said. I have to test a few more sites, but so far it solves the problem when browsing (tested NY Times and CNN).
So weird that muted videos somehow sort of sends an audio stream to the N8.
What was the setting and where was it located so others can find it?
In the Safari extension (that you buy in the App Store) “StopTheMadness”, there is a setting called “ Stop autoplaying audio and video”.
Apples own setting is bypassed by some sites, and especially the ads, so buying the Safari extension seems like the only solution right now.