You may not realize that in a given field, the same variable that represents the same basic thing may be negated depending on the part of the world the paper is

You may not realize that in a given field, the same variable that represents the same basic thing may be negated depending on the part of the world the paper is published from. This can be fine, if it’s your subfield, you happen to know to be careful with said variable. I don’t personally dig into a lot of disperate maths in different papers very often, but this is the single biggest complaint my polyglot friend talks about. The second biggest is when he has to read and parse the math from a dozen unrelated papers in a field to find out what some random undefined variable means in the actual paper he cares about.