Your Porter comparison seems about right. That depth isn't ideal, but it's still an incredibly useful station. The same would be true for NSRL stations. A more modern example would be the Grand Central Madison terminal, which is similarly deep. I haven't been yet, but it looks nice, and is an example that it's possible to quickly bring a
ton of people up to street level or subway connections.
Again, that depth isn't ideal. It adds time for people, and slows passenger flow. Sadly, if we had built NSRL during the Big Dig, the
plan had these stations much closer to the surface. At the Central Station, the Blue line would have been just upstairs, instead of a ten story escalator ride.
True-ish, but that's because most of Downtown Boston is exceptionally vulnerable to climate change. If Central Station is flooding, then so is everything around it. We will need to build protections against rising sea levels, and those will equally protect any NSRL. If he's saying we shouldn't build new infrastructure downtown because of climate change, that sounds like his plan is to just... I don't know... abandon Boston to the sea?
And besides those points, a lot of what Straus is saying is just kind of dumb. His concern over climate change is undercut by the fact that his proposals for what else to build are mainly (by cost) car infrastructure, which is already the biggest part of Massachusetts's GHG emissions. He spends a lot of effort criticizing what is or isn't in the new Kennedy School study, but that hasn't been published yet, so I don't even know what he's looking at. While dismissing that report he hasn't read, he does give a lot of weight to some undergrad class project at Harvard from a few years ago (they apparently found that a monorail between north and south stations would be just as good as NSRL, to give you an idea of the quality of that work). And he belabors the details of what goes into NSRL, I guess to make it sound more onerous (We'll also have to build approach tunnels! And escalators!).