Does it work if you disable favicons? (I disabled favicons when I set up the computer, but for a different reason; it is a feature that I don't use.)
If websites can detect that you've disabled favicons, then you are easy to track between all websites because you are very unusual.
I don't think that's true. You'll just look like someone who already has it cached.
It depends on how the browser rejects favicons? If the browser reports the icon is already cached, I agree (assuming the reports are indistinguishable). But maybe it just never downloads the icon, for example.