I don't know if they have to agree or not. It's a matter of having a way to associate accounts, and I don't think that the StackOverflow API allows for that. Then the browser adds the tip button in the address bar or within the UI as it does on Twitter:
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I don't know if they have to agree or not. It's a matter of having a way to associate accounts, and I don't think that the StackOverflow API allows for that. Then the browser adds the tip button in the address bar or within the UI as it does on Twitter: