"I'm interested in opinions on this: do you believe that a variable with a const qualifier should automatically go in code?"

Let me repeat my earlier quote from K&R:
"the compiler should warn if it spots an attempt to modify such a variable, but the effect of const is otherwise implementation-defined (see K&R)."

I also said,
"const is commonly used by embedded compilers to indicate fixed values to go into ROM;"

For once, I omitted to add "you need to read the manual for your particular processor"