I wrote an essay in response to what I consider the most interesting parts of this paper:

Two Lightning Attacks Analyzed: A Response to John Light #351788

TLDR: both of the attacks John identifies are not serious in my opinion. They do not support the thesis (which I probably misunderstood, and which he probably does not claim to make) that all lightning users actually trust a third party not to steal their money, which, if it was true (I don't think it is), would imply that the lightning network is actually a giant custodial system.