I think rebol’s human language power comes not necessarily from its syntax, which is more functional in style than English-like:
head remove back tail insert head copy blk last blk
I think the language power comes from the ability to create your own dialects, little declarative mini-languages or markup languages which can be about as English-like as you want.
Rebol’s syntax is pleasant in that it’s clean and removes most symbols/punctuation, but I don’t think it’s a significant selling-point either way. People who are willing to write code are typically able to overcome syntax challenges. I still can’t believe how popular regular expressions are.