> leading people to mess up nested matches frequently.

Very often this leads to typing errors. Otherwise it's caught by autoformat (which everyone should be using). But even without that, this is one pitfall every OCaml developer is aware of.

I'm not arguing the syntax is perfect, but I wouldn't say it has a serious problem because of that. Never seen that being a problem.

Keyboards are also extremely error-prone. I can't count the times where I mistyped because of that. After each keystroke, people should type a "confirm" character in order to make sure of what they're doing.