Single quotes are only required when:
a) The value contains special characters like spaces
b) The value must contain lower-case characters (and CASE(*MIXED) is
I think point b) contradicts that first bit. It seems to me that, if I
understand correctly, the solution to the problem that the developer had
(which is a variable being interpreted as a literal if the & is forgotten)
is to use mixed case for variables.
Maybe I misunderstand what you are saying, but the point of b) is that
text literals are interpreted as (converted to?) upper case unless you
enclose them in single quotes.