A lot of IDE configurations, such as VSCode on the default config, highlight Unicode characters that are invisible/look like others (eg. cyrillic characters or non-breaking space) or even all non-ASCII characters, regardless of whether they're in a string or not.
In either case, it would appear as added code, not different characters in the same code, so maybe about the same. If someone changed one character in an existing string though, I think it would be more likely caught visually by someone used to seeing accidental garbage show up
