That logic sounds fishy to me. After all, they took C++'s semicolon syntax over Haskell, OCaml and Ruby's semicolon-free syntax, so there must have been a reason for picking one over the others. So the issue is not about inventing syntax, it's about choosing one (existing) syntax over another.
pcwalton says it was to attract C++ devs, which is interesting considering that Go was also designed to attract C++ devs and made the opposite choice. As a sometime C++ dev, I recognize the historical uselessness of semicolons and would love a replacement language that did away with them.
Since when OCaml is semicolon-free? It not only has semicolons, single semicolon (;) means something different than double semicolon (;;). The former is used as an expression separator, like comma in Erlang, and the latter denotes the end of a top-level declaration, like period in Erlang. That's a pain while refactoring, but I can live with it. Anyway, that's just a style, nothing more, you can learn to love it or you can write a "transpiler", it's really a non-issue.
True, Ocaml has semicolons, although it's a little different given that you can construct deeply nested functional expressions without ever using a single one. If I remember correctly the semicolon is a separator, not a terminator, which means that declarations don't need to end with a semicolon, for example, and you pretty much only need it to separate statements.
I'm not sure I prefer 'in' over semicolon in declarations. I mean:
let x = ref 0 in
(* something *)
in Ocaml is not much worse/better than
let mut x = 0;
// something
in Rust. As I said above, that's really a minor, stylistic issue, one probably would write "let x = mut 0 in" for a week or so (coming from OCaml) and that's it, after a week it becomes as natural to write semicolon as it is to write 'in'.
pcwalton says it was to attract C++ devs, which is interesting considering that Go was also designed to attract C++ devs and made the opposite choice. As a sometime C++ dev, I recognize the historical uselessness of semicolons and would love a replacement language that did away with them.