There's a really good argument to use plaintext - it lends itself to very efficient use through searching, matching and replacing, whether interactively or in bulk. The lack of structure and semantics in a pure plaintext representation is often a curse, but sometimes a blessing.

At the same time, I'll go further than you, GP and GGP - I'd say that insisting on coding in plaintext, specifically on always directly reading and editing the same plaintext, single-source-of-truth representation of a program, is fundamentally limiting our ability to manage complexity, and makes people waste a lot of time on faux-problems like "lots of small vs. few big functions", or "exceptions vs. result types", etc.

FWIW, plaintext is still okay for most coding use cases - it's trying to fit everything into the same source code and somehow keep it readable that's an impossibility.