Modifying the program is not inherently harmful,
Not inherently harmful? I'd say a large percentage of bugs in programs comes from the fact someone modified the program. That's my point. If something is not broken, don't fix it.
but the fact is that it prevents a lot of subtle bugs that might not come up in normal debugging at all.
It was
given that the program was working. I assume that the OP doesn't mean "it has bugs" when he writes "working".
Adding strictness on a working program is a bit like rebuilding the Egyptian pyramids because originally the construction workers weren't wearing safety harnesses.
Abigail