Take for instance "but you're still going to be dropping performance on the floor vs other I/O models as you get into the 1000s of connections"
Notice how it was written in passive voice, without any references to personal or 3rd party experience, and with nebulous hand-wavy numbers which can literally mean anything ?
Well, he had to write it that way because he could not find any hard evidence to back it up anywhere, could he ?
Here's some "reasonably sounding" information for you: builtwith.com reports that one eighth of the 10k largest web properties run Varnish.
They would hardly do that, if performance "dropped on the floor" with "1000s of connections", would they ?
You know what an actual Varnish users commented about performance after deploying Varnish on one of the worlds largest news sites?
He made jokes about the servers being so bored that they were making grilled cheese sandwiches.
No that comment is classical trolling: Technically sounding bla-bla, based on random google results, but totally removed from the legitimate and relevant critiques actual Varnish users bring.