[sbov]

For what the OP is talking about, I would say to never attempt a rewrite.

The only caveat is if you have spent the time to truly understand the codebase, then maybe you can do it. Most people advocate a rewrite because they don't WANT to understand the codebase. Even if you understand the codebase, it's pretty dangerous, but at least you have some idea of what you're saying you will rewrite.

So yeah, it can happen, but if you are in the situation that you have the knowledge and experience to override that rule, then you have the knowledge and experience to know that you CAN override that rule. It sounds a little circular, but it's how I tend to aim my broadly-given advice. If someone knows what they're doing, they should be able to recognize when they can ignore your advice. Anything else would have to be tailored to each specific instance, which isn't plausible in a blog post.