I like the Arkell versus Pressdram.

https://news.lettersofnote.com/p/arkell-v-pressdram

That is excellent, and if you enjoyed it, you might also enjoy the Cleveland Browns one:

https://news.lettersofnote.com/p/very-truly-yours

The cc: to Art Modell [0] was a nice touch. He was a real character. I imagine he thoroughly approved of the response, assuming he didn't think of it himself.

[0] https://en.wikipedia.org/wiki/Art_Modell

that was lovely. Sure enough the letter writer has a wikipedia article as Paul Devlin (filmmaker)

There is a reference to a "small grammatical error" in the rejection from Harvard, but I did not quite understand what he was referring to.

Was that obvious from his reply and I missed the point?

I am guessing it must be in the form of "Please accept our letter of rejection" or similar?