For security we're not willing to change anything except the link colour on visited. If we do anything else we'd end up with being able to write programs that could check whether you've visited a link by checking the page rendering time of a page that has thousands of identical links. So if any specification says anything that contradicts that we'll purposefully violate it to protect your privacy.
Bug 1674988 Comment 1 Edit History
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For security we're not willing to change anything except the link colour on visited (and we'll even lie about that if you try to check it programatically). If we do anything else we'd end up with being able to write programs that could check whether you've visited a link by checking the page rendering time of a page that has thousands of identical links. So if any specification says anything that contradicts that we'll purposefully violate it to protect your privacy.