Enthusiastic second for the idea of explaining this in the documentation. Also it seems like his line has shifted a bit; on one of the bug reports he says:
and on a later one
which is not quite the same, as the first one would suggest that “4 - 2 * 6” would evaluate mathematically when used in-line.
In fact… the symbols do evaluate differently from the words, but not in the ways one would expect. Consider:
When play begins:
say "6 - 4 / 2 = [6 - 4 / 2]. 6 minus 4 divided by 2 is [6 minus 4 divided by 2]. 3 * 2 + 1 = [3 * 2 + 1]. 3 times 2 plus 1 is [3 times 2 plus 1]. 4 - 2 * 6 = [4 - 2 * 6]. 4 minus 2 times 6 is [4 minus 2 times 6]."
Lab is a room.
So the first pair is behaving as Graham said on the first bug report–when symbols are used, the / is evaluated before the -, but when words are used, the operations are evaluated from left to right.
For the second pair, when symbols are used, the + is evaluated before the * even though the traditional mathematical order of operations is the other way around and even though the * is first–that is, the result of using symbols is neither linguistically nor mathematically correct, in Graham’s terms. (And the result of using words is both.)
For the third pair, when symbols are used, the - is evaluated before the *, which obeys English rules (operations evaluated in order) but not mathematical ones. When words are used, the times is evaluated before the minus, which obeys mathematical rules but not English rules. This is the reverse of what Graham’s first note suggests.
In none of the cases are the operations consistently evaluated in order, which is what Graham’s second note suggests (about linguistic rather than mathematical rules applying outside of equations).
So I’m completely at sea both about what the desired behavior is and about what the actual behavior is. Some clarification in the documentation would definitely be helpful, and it does seem to me that this can’t all be working as intended.
In the meantime, it’s definitely prudent to put parentheses in when in doubt.