[ironmagma]

The answer is, anyone who can. If you’re a random statistics professor but if you’ve somehow managed to build the capability to speak coherently about physics and mostly know what you’re talking about, you should be commenting on physics papers, regardless of the fact you’re “not a physicist,” because of your pedigree. You might find a serious mathematical error. The thing is, we tend to call people who do that in a way that’s good, “physicists,” so it’s a chicken-and-egg situation.