[flatline]

> no change in runtime behavior

That's the problem: how does the maintainer guarantee this? And when flooded with multiple such PRs, the task rapidly becomes overwhelming. If you have a robust suite of unit tests and a CI system you have better guarantees but still about as much work to ensure the new functionality is properly tested. That's not to say the maintainer's attitude in this case was excusable, but it's his project and this style of maintenance is definitely not for the feint of heart.

[eropple]

In many cases, you're right. But here, specifically? If somebody goes through your code and annotates it with types, TypeScript is gonna scream if it doesn't build clean and is going to emit the same code it did in the first place. This is literally complaining that somebody might write helpful documentation for your system and that you'd refuse to merge it. It's a pathologically bad statement.