Currently, a topic that's both locked and moderated displays only the locked icon. But unless and until the change allowing mods to reply to locked topics is undone, I think topics that are both locked and moderated should show both icons.
I vaguely recall some conversations here about these icons, but don't remember exactly what they were about. However, I don't recall the conversations being about whether or not both icons should be displayed, and I now think that they should. I myself was not aware, until I tested this recently (as part of Bruce's issue with wayward mods replying to locked topics), that "locked and moderated" was functionally different from "locked." I now realize that it is. And a mod who replies to a locked topic may wonder why their post is not appearing immediately. Although Nina has just added this to the docs (thanks, Nina), unless the icon actually appears I think mods will wonder what happened.
Of course, Mark is now considering undoing allowing mods to reply to locked topics. But unless and until that happens, I think both icons should appear.
Messages are the sole opinion of the author, especially the fishy ones.