Because he used the alt symbols, probably.

"Tilde" is one of those words I usually only read, don't say, but when I read it to myself I call it a till-dee. I think I've heard it that way down here.

I just looked it up. Webster has til·de \'til-d e. . .well, let's try that again. Nope, can't do it.

No way to make that upside down "e" that sounds like the "u" in "abut." No hexidecimal code for it, no html for it. And when I was looking for it (all in the effort to post a pronunciation of the word "tilde") I found, in my 1987 Webster, that they call it a "swung dash"!!

SRS