Only one character is going to be marked in this case, not a whole line or section of code. Deleting it and retyping it costs one second. I guess I've seen more than my fair share of encoding issues. I used to tutor at a university, so students were constantly coming in with code they'd copy/pasted out of their assignment (usually a Word doc) or from a web site.
I think that's a great argument. If someone mails the code, I hope to have the cleverness to suspect the encoding. However, I thought about a code repository or similar where this may be an issue, but most often is not. And I have seen some code where a wrong language character did not provoke a reasonable error, but some arbitrary parser error that went off in another line altogether (not necessarily C#).
