[moring]

Doesn't the article show that newline isn't harmless at all?

Of course EOT doesn't end anything by itself, nor does 0x0a end a line by itself -- all that happens through code that interprets those characters in a particular way, so talking about the "danger" of a character in absence of any code that operates on it is meaningless. In the presence of code, on the other hand, "harmless" in the extreme sense means "there exists no code that will act up when presented this character", which the article shows to be wrong.