I guess the other well-known syntax form at the time was the one in the Algol/Pascal/Ada/Modula-2 tradition with keywords (begin/end, if/endif, etc) for structu

I guess the other well-known syntax form at the time was the one in the Algol/Pascal/Ada/Modula-2 tradition with keywords (begin/end, if/endif, etc) for structuring blocks and that's what MOO cribbed from, while LPC (and later JavaScript, Java, etc.) did the braces thing. At the time I liked braces a lot more but since then have come around to preferring the more Wirth-ish style. I think Julia has shown that a dynamic lisp-ish language can do this very elegantly.