I was prompted to "move this discussion to chat" because of taboo extended discussion in comments. But I don't want to do that because I want the comments to stay there. Instead, I want to start the same chat manually, inviting the question OP. Is this possible?
Per OP's request, I am expanding what I said in the comments to an answer.
According to this answer, if you click on "move comments to chat", then the comment both remain on the original post and are copied to the chat room. (Of course nobody prevents the comment author from deleting the comments later.)
As you confirmed in a comment, your own test seems to confirm it. Here is link to the chat room and link to the comments. At the moment the first messages in the chat room and the comments under the post seems to be the same. (The comment saying "Let us continue this discussion in chat." was not copied. And, of course, new messages added after creating the chat room.)
Still, I suppose that in some situations it might be preferable to a create new chat room or to discuss this in an already existing one. (If you want to have the comments there, the only possibility I know of is to copy them one by one as I did here to show an example.)
If you want the user to come to that room, you can ping them in a comment and add a link to the room or you can invite them via their chat profile. (Keep in mind that if you want to invite user to an already existing room in this way, you have to be in that room.) See also: How do I invite a user to chat?