Just look at the response: It is very clear that the Quarkchain team is avoiding the problem, nobody says it is a node. The team is just trying to manipulate people who doesn't fully understand this technology.

“If one of the shard in state sharding is compromised, then the tokens stored in that shard might be lost forever and could not be recovered. This is called a single shard takeover attack and the same has been discussed in Ethereum FAQ. In transaction sharding, recover is possible since each shard store a complete global ledger.”

Response: We respectfully disagree with the claim here. First, a shard does not mean a node. A shard is a blockchain run by many many nodes from different clusters and each node in a cluster has a copy of the full ledger of that shard. Please see QuarkChain whitepaper Figure 7 (a) and (b) for a detailed example. In addition, Ethereum sharding is also working toward state sharding direction.