Oh, I still hear ads giving URLs with inexplicable backslashes in them. "Visit our website at foo.com backslash baz"
I feel like I hardly understand the idea, because a / and \ is just as distinct as a b and a p. We don't make mnemonics for those?
Can confirm. Just yesterday on NPR.
The average person does know (or at least should know) the difference between an exclamation mark and a question mark; it's part of literacy. One could argue that knowing the difference between a forward slash and a backslash is part of digital literacy (and that it's a worthy goal for the average person to have digital literacy).