The whole point of introducing a math equation in a paper is to serve as a completely unambiguous formalism, devoid of the ambiguities of the spoken word.
And yet, it is all too common to read something many times and not make sense of it, until it hits me the author means something completely different than what the symbols would imply in principle, and what looked like a formalism is basically a sloppy direct translation of words as math symbols, combined with abuse of notation, idiomatic but undefined uses of established notation, or outright nonsense.