> I don’t recommend that people use Go to write complex multithreaded code that accesses shared state. My point is that I doubt many people are doing this while erroneously thinking that their code is guaranteed to be memory safe. In other words, whatever the problems with Go may be in this regard, it’s not primarily the absence of an ‘unsafe’ keyword that’s the issue.

I think the point here is that if the word "unsafe" exists as a language construct, someone is not wrong in assuming anything without that mark is safe. Otherwise, why isn't there a "safe" language construct?

That’s true to an extent, but it’s important to bear in mind that you can’t lexically scope memory unsafety. Rust code that doesn’t contain an 'unsafe' block should be safe assuming that all of the libraries it’s built on are safe. But those libraries may well contain 'unsafe' blocks that are (one hopes) carefully written to be memory safe.