You are pointing to the unique and quite narrow exception to the truth defense that was introduced in 1974.

I pointed to two classes of exception: the spent convictions exception (which is certainly narrow, but an exception nonetheless), and the more general class of exceptions for defamatory implications too.

When people say that British libel law is tough, what they mean is not the written law, which is essentially the same as, say, American law, but the interpretation of the law;

I think you've got the wrong end of the stick. SaidAchmiz & I weren't doing a comparative study of libel law. SaidAchmiz, as far as I know, was just using "slander/libel" (without having a specific country's laws in mind) as an off-the-cuff example of truth being an absolute defence in the real world. I said that this wasn't true where I happen to be, leading into my bigger point that something being literally true oughtn't be a universal justification for saying it.

I didn't read SaidAchmiz as making a point about British libel law being written/interpreted stringently. I was attacking the empirical claim that truth is an absolute defence in libel cases, and the normative claim that truth being an absolute defence in libel cases is "instructive" about truthhood being a universal defence against criticism in everyday life or on LW.