if a reply is moved to a new topic, then new responses to the topic aren’t notified to the owner.
I’ve tested this on https://try.discourse.org/. When a post is moved to a new topic, the post author’s notification level for the new topic is set to Normal. I would expect it to be set to Watching.
2 posts were merged into an existing topic: When a post is moved to a new topic by a moderator, the moved post’s author does not have the «Watching» notification level for the new topic