When a post is moved to a new topic, the followers (those who watched the topic) of the original topic becomes automatically followers of the new topic (the moved reply).
while the notification level for the new topic should be set to Normal for users other than the original poster.
Continuing the discussion from I get notifications for topics I haven't chosen
This is by design, @gerhard recently worked on this. The users expressed the will to watch the original topic so we assume they want to watch the new topic.
aha, thanks for the declaration.
I can argue that most of the times, they don’t. because the new topic is something that doesn’t fit in the old one, otherwise it won’t get moved into a new topic.
I can share our user experience on this:
as a user during the past week, I was getting some notifications I didn’t want to! this happened for some of users as well, described in this topic: https://meta.discourse.org/t/i-get-notifications-for-topics-i-havent-chosen/129187.
our users complained us about it as we have violated their privacy by sending them notifications they didn’t chose to received!
I think privacy violation here is a bit extreme of a position to take here.
Going to leave this to @codinghorror to decide, I am on a fence. May take him a while to reply here as he is out.
Assuming:
User (A,B,C,D) are watching topic X
User B posts
User C posts
User D posts
Mod splits off B,C to topic Y
Option 1 (currently happening)
A,B,C,D are now watching topic Y
Option 2
B,C are now watching topic Y (A,D are not)
Option 3
(something else) B,C watching topic Y, A,D tracking?
Jeff your call as to what you want here.
I agree that this is not a privacy violation, no matter how loud they state it. But I liked that post because of this logic:
So only the posters who are already discussing something different should watch the new topic:
I corrected the option by changing B to D
maybe I’m using a wrong word/context. their criticism was of course for us, and not to discourse. what they have said to us was this:
we feel that you are not respecting our interests, and you’ve forced us to follow some topics from specific users*!
{*we have 2-3 specific users with extra activity in our forum, who sometimes start extra discussion in a topic and we need to move their replies into a new discussion!}
It seems there is only two options on the table, new way or old way, but in both ways the system decides.
I know there are holes in the following ideas, but it is just a compass bearing and not a detailed map.
Perhaps instead of the system deciding a new user option is added that allows a user to decide when a post is moved if they follow those post automatically (I think of this as the passive option).
Another option is that they are prompted when they visit either topic again and choose which of the post they want to continue to be notified. (I think of this as the active option).
I think that subscribing to the new post all users that have been subscribed to the original post is the correct solution, as it is now.
The users have not control of when an admin or mod can split a thread.
If they are interested in the theme of the post that is split, and they are not subscribed to it, they miss the opportunity to read what other people has to say, or even read that post if it is spitted before they read it, so they cannot know if it is of interest for them or not.
If they are subscribed to it and they are not interested, they always have te opportunity of unsubscribing from it.
I agree with Remah, any user whose post got moved to the new topic should watch, everyone else should be left untouched.
@techAPJ can you make this change?
Problem is that in this situation there is not a good or bad solution. When users are watching or tracking specific topic and post is moved to another topic, some users want to be notified about changes to that new topic and some don’t.
We decided to revert that change and simplify codebase because that adjustment added a lot of complexity to support that edge case. Therefore, when the post is moved, the user’s current notification level will be carried on to the new topic.
disagree.
when a reply is moved to a new topic, it means it is considered off-topic for the previous discussion, and it’s better for it to be a new topic. why should users be interested in off-topic discussions?
Understood, unfortunately you are going to need a custom plugin here to change this. The logic is far too complex to maintain this edge case and the change was causing other serious bugs.
The software has no idea if you are splitting stuff off cause it was
One could argue that if nobody cares about it, you ought to just convert it to a PM or delete.
exactly! that’s why if a reply is splitted and not deleted, it means that it worth and others can care about it; if they choose.
got it 
Maybe I chose to follow that topic because of that reply.
I’d rather have a notification too many than one too little. And I can always choose to unfollow the new topic then.