`wat(foo)` also works. The author says he implmented the `wat / foo` syntax to allow you to more quickly use wat by avoiding parentheses

Probably so you can run a big complicated formula in the REPL and easily prepend `wat /` to it to inspect what's going on.

Same reason jupyter notebooks allow you to prepend '?' or '??' to inspect a variable (though not expressions, in that respect this syntax is better)

I get the reasoning behind it, but the choice of the division operator is still a little weird.

I believe it should be equally possible to overload the bitwise OR operator (|), which, for people used to piping in Unix, is probably more intuitive.

Wrong direction: you‘d „pipe“ wat through the object. Although TiddlyWiki users might feel right at home.

It could override the reverse bitwise or magic method `__ror__`.

Right, that would be a wrong pipe direction. Fun fact: It's already possible to do "wat | foo" or "wat << foo" (if you're more familiar with C++ iostream), it has the same effect as "wat / foo"