The bolded point above by Vitalik is that if transactions are free up to the burst limit, then the DoS attackers can avail of it. Thus the DPoS blockchain is attacked and not just the servers (nodes) on the periphery. A sock puppet attack can be employed to defeat any attempt by the block producers to fairly limit each user. This would have the effect of forcing all users to the minimum transaction bandwidth their stake will accord, because a significant portion of the stake is maxing out the bandwidth and compensation of the block producers.
Here's the blue part you highlighted, and it's going off wrong assumptions. he assumes minimum transaction bandwidth is bad.
Calling it "minimum" makes it sound bad, better name is
guaranteed bandwidthIt's literally your expected transaction bandwidth. Anything else is just nice luck and not important. And
no spam attack can take away your guaranteed bandwidth. This is not the case on fee based blockchains.
Blockchain operates under assumption of 100% spam attack and has 0 issues. There is no burst limit, it's lucky free bandwidth no one cares about.
A sock puppet attack would do nothing since bandwidth is divided from maximum bandwidth per vested coin, not per account, so irrelevant.
You didn't have any good points this time around and didn't read my points, so not worth addressing.