The thing is, these symbols are supposed to represent something, so it's better if they give some intuition. But some words get overused, exactly because of that.
E.g. the two Rs we are talking about here both stand for the same word - Real. Except one is Real as in the Real numbers, and one Real as in the real part of a complex number.
If you go with a random symbol, you're putting a different kind of cognitive overhead because you have to map a random symbol you never saw before to a specific concept. Here you just have to distinguish font, and even that is often not necessary, because you often are dealing with a branch of maths that only uses one of the meanings.
E.g. the two Rs we are talking about here both stand for the same word - Real. Except one is Real as in the Real numbers, and one Real as in the real part of a complex number.
If you go with a random symbol, you're putting a different kind of cognitive overhead because you have to map a random symbol you never saw before to a specific concept. Here you just have to distinguish font, and even that is often not necessary, because you often are dealing with a branch of maths that only uses one of the meanings.