This is likely borrowed from Haskell where functions starting with special characters are treated as infix. Parens and backticks allow for switching between the conventions

    add a b = a + b
    -- these are all the same
    3 + 4
    (+) 3 4
    add 3 4
    3 `add` 4

The article might also make slightly more sense in context, I think it was in part an idea for how to make infix notation more useful in Kitten: https://github.com/evincarofautumn/kitten/issues/174