Earlier quoted context omitted.
Conversation about semicolons? During a job interview? I'm sorry, but this is a waste of time. Why don't you talk about, you know, algorithms? Concurrency? Databases? Testing? Or anything that is more than remotely relevant to the job?
"It's the purest test of Language facility" None of your alternatives "algorithms? Concurrency? Databases? Testing?" really test language facility. Those are important, and they have their place in the interview process, but so does language awareness.
And anyway, what better test of language facility is there than having the person code something? Or looking at code they've written? Whiteboarding is a weird, artificial environment that's not going to represent the coder's natural behavior in the wild.