For number 1, I think it deals with the idea of PoS, where number of stakes represent the power and responsibility an individual has within the network. Blockchains rely on not single, but distributed multiple nodes securing the network. Self-bond is a good number to see how much stake this validator has in the game, but too much in one basket also represents a big risk.
Number 2 and 3 are the risks which delegators cannot really see unless an accident through bad infrastructure happens (large downtime or even double sign). The history of Cosmos Hub is quite short so there is no real good reference except Game of Stakes of past testnets to see if these validators were actually thoughtful about their set up.
For number 4, yes it is a double-edge sword and I think it will take time for the market to choose reasonable ‘pricing’ for their services. But still, for us, 0% means ‘no pricing’ which would disrupt the market and not provide any incentives which was the original design of Cosmos.
To me, the reasons you mentioned are actually supporting the idea of how it is not very good to have 0% commission fee. Yes it is best if validators act upon the thought that no value is added in long run, but if this continues, I think suggesting this idea would be helpful before things are too late