- Rewrite Code From Scratch has good discussion of reasons to rewrite and reasons not to
- Things You Should Never Do, Part I is the commonly-cited argument from Joel On Software
- Re (tilly) 1: (OT) Rewriting, from scratch, a huge code base has discussion on when rewriting may be a good idea. It seems like there's more conversation in this thread, which I haven't read.
- code quality - When is a BIG Rewrite the answer? - Software Engineering Stack Exchange is a good answer, specifically calling out that the challenges are sometimes organizational rather than technical
- Repeat yourself, do more than one thing, and... — programming is terrible reminds us not to be mindlessly dogmatic
- Lessons from 6 software rewrite stories - Herb Caudill - Medium is a good read, covering several stories aside from the Netscape rewrite which Joel focuses on.
tl;dr "don't rewrite from scratch" is usually good advice, except when it's not, and sometimes the reasons for the decision are organizational/cultural rather than technical.