I would actually say that in that case, the comments are just no longer needed and don't need to be moved to chat. The idea of moving to chat, for me, is to give a space where extended discussion can take place (sure), but if the discussion isn't looking like it's going to end up improving the post... (e.g. the comments are just opinionating on things), they don't belong in chat.
What goes to chat should be extended discussion that *does* provide further value to the question or answer eventually.