IMO it doesn’t matter whether an algorithm is “serious” or not, it depends solely on how people treat it.

In this story, ROT13 is taken seriously, so it is a serious algorithm. And the creation of such a good version does have it’s value, no matter how useful ROT13 is.

Rot13 is not Caesar's cipher. Rot13 is in the family of rotational ciphers, but it's a more modern concept designed around a 26-letter alphabet (so that running it twice produces the plaintext again)

Sure it has its uses for simple obfuscation but in that case my central point is relevant. It's only good for obfuscating ASCII letters.

Btw what's commonly known as Caesar cipher (aka shift cipher) is a generalisation of Caesar's original cypher (described as shifting each character 3 places). ROT13 is different from the "original" as it shifts by 13 characters over a 26 character alphabet. This makes the encode and decode steps the same.

You can play with different alphabets and shifts here: https://crypto.interactive-maths.com/caesar-shift-cipher.htm...

As an aside: After 20 years of IRC usage I read and write rot13 without any technical aids (mostly due to the first 2 years of quakenet). I wouldn't be surprised if you'd find someone who can speak it :)