I made a program that tells what control characters are in the Mac OS ROM file. It reported that every single control character is in that file. Then I had it only look at the bootscript part. The carriage return and line feed characters are the only control characters found there.
http://www.ascii-code.com/ This page will tell you what the control characters are in case you don't know.
I added some code to the bootinfo_init_program() function in bootinfo_load.c file that changes all control characters to '\n'. This made Mac OS 9 boot. But when I changed the control characters to a single space, Mac OS 9 failed to boot. This seems strange to me. The space character is the ultimate whitespace character, so why would it fail when '\n' succeeds? My only guess right now is a bug with one of the words in Forth.
Here is the code I used. It is found around line 190 in the file:
while (current < size) {
c = base[current++];
// remove all control characters if (c >= 0 && c <= 31) { c = '\n'; }
if (c == '<') { script = 0; tag = 1; taglen = 0;