[nauticacom]

    I can hold the whole language spec in my head while I'm programming

People love to say this about Go, but it's not something that, like, actually matters (and I doubt it's literally true). A language can be reasonably understandable such that you can effectively and productively program in it without being aggressively simple. Again, to use the case of Ruby, I might not remember every single syntactical construct or handling of every edge case, but the language is reasonably understandable such that I can write programs without constantly asking "what was the syntax for that?" or "how do I express this?" As a counter-example, I think the complexity of C++ is not just limited to its implementation, and leaks out to its interface.

    ...sacrifice the simplicity of the language, or make it any harder to read go code

These are two separate concerns which, while somewhat related, are not directly correlated. A simple language can make it more obvious which syntactical constructs are being used and what literal operations are being performed, but there are many more dimensions to reading code than just those.