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I think a majority of the witnesses have actually concealed their identity, so that's already a huge +

Really? Not those currently in the top 20. And not even for the next 20.

well it's definitely not common/open knowledge looking at their profiles, I don't doubt you got more info ;)

It's not just in their profile that you can find this kind of information. The blockchain is a (public) goldmine in this regard.

That is of course true, but I wonder if it is enough to definitively identify someone