We talk about unicode codepoints, bytes, characters, and just the word "length" to describe how long a string is allowed to be. This is confusing at best, so ideally we pick a unit and stick to it.

Some areas may require an MSC to make uniform.

An example of where this is a problem is state keys: They're limited to 255 bytes but user IDs are limited to 255 characters, so by extension 1 character == 1 byte because otherwise membership wouldn't work.