Poor choice of wording on my part. I meant to say that comparing moralities is one of the things that meta-ethics covers; that if you are engaged in comparing moralities, you are doing meta-ethics. Is this wrong?

I think it is. Comparing moralities is part of morality. Comparing meta-ethical claims such as moral realism, emotivism, error theory, relativism, etc. is meta-ethics, of course, but if you're comparing object-level moral systems, like any of the various flavours of "utilitarianism" or any religion's moral teachings or anything else, then you're doing morality, not meta-ethics. True, you are asking "should" questions about how to answer "should" questions, which is rather meta, but that's not the kind of meta that "meta-ethics" usually refers to.

(That's not to say that meta-ethics is irrelevant to comparing moral systems — if you have a coherent meta-ethics, then it'll probably inform your comparisons — but it's not essential to the process.)