I'm all for people doing what they feel works for them, but none of the stated arguments (either from the author or direct quotes from the original tweeter) hold up to scrutiny.
The joke is that who would ever actually use their monitor in a diagonal orientation? It's funny that someone actually did it, that's all.
Humor is usually subjective.
I have to disagree on this one. Most jokes that I have heard or read weren't funny at all. And seeing that I'm a dad, most jokes that I tell aren't funny either.
It’s less of a joke and more of a “huh, isn’t it curious this is possible”