That was a reply to "Generics don't solve immutability" which was a reply to a post that did not contain the word "immutable" but does contain the word "generic

That was a reply to "Generics don't solve immutability" which was a reply to a post that did not contain the word "immutable" but does contain the word "generic" James' comment you quote was responding to your comment, which he parsed generically as "Generics don't solve T", with a comment of the form, "Generics make it possible to implement a generic T." I'm confident you can read, but I'm not so sure about your reading comprehension and critical thinking.