I think the audience already understands why it works, it's more the knowing there's a relatively small set of mnemonics for these things that's interesting. "eyJ" for JSON, "LS0" for dashes (PEM encoding), "MII" for the DER payload inside a PEM, and so on.

I've been doing this a long time but until today the only one I'd noticed was "MII".

The audience yes, but the author clearly seems to not understand it when they wrote this the first time.

> I did a few tests in my terminal, and he was right!

He clearly had no clue how base64 worked. You don’t need a test, if you know it.

> As pointed out by gnabgib and athorax on Hacker News, this actually detects the leading dashes of the PEM format

They needed help for this. I’m not sure that they opened Wikipedia at last to understand how base64 works even now. The whole article has an “it’s magic!” vibe.