Why I was interested is summed up here:
[...] Anonymity is, and always is, a social norm. There is no plausible context in which anonymity exists without social norms that support the respect of it. There is nothing unique or unusual about internet anonymity in this regard. The expression here suggests that any attempt to promote or maintain a norm of respecting anonymity on the internet is pointless, because it’s not capable of being technologically guaranteed. But again: the lesson here wouldn’t be to give up on anonymity on the internet, but to give up on anonymity in any social context in which its valued, for any reason, because of the possibility of breach.Brian Leiter wrote a letter to a guy's bosses - including all his contact information in a blog post - for "insolence". Can you beat that?
In the real world of the internet, of course, anonymity is alive and well. Millions of people participate in it as a social practice, and a vanishingly small number of them have their anonymity breached. The norm is reasonably well supported most of the time. Norms retain value when they’re generally honored; no norm is universally respected in all cases but that doesn’t vitiate their value. That’s why Leiter’s behavior should be interpreted as a threat to anyone who values this norm, and why it’s important to push back against this kind of behavior. Norms retain their value and power when there are costs for violating them; costs Leiter has so far successfully avoided.