MyBB Community Forums

Moderators can change subscription preference of thread starter,
They do that in my forum unintentionally - they have certain general subscription preferences which is selected automatically when they create a thread.

When they change thread, that option gets selected automatically.
Although they make no change there, even when they change a single character in thread, their subscription preference applies to thread's starter.

Example :

1. user A creates a thread
   
2. user A doesn't subscribe his own thread generally (via usercp options)
   
3. user B subscribes every thread he created/posted
   
4. user B gets private message everytime someone posts to threads he subscribed.
   
5. when user B makes changes on user A's thread, his subscription preference applies to user A.
   
6. user A gets private message when someone replies to thread he isn't actually subscribed to.
   

What kind of changes? Do you mean editing the 1st post only or something else as well?

May be related to the cause of https://github.com/mybb/mybb/issues/2060

We have index thread in our forum, when someone creates a new topic moderators update that index thread.
I noticed this happening on this thread, created by me and updated by different moderators. I had 0 subscription before, I started to have different subscription preferences for different index threads edited by different moderators. Their preference applies to me.

So when a moderator who subscribes to every thread and gets private message when someone replies updates my thread, I started to get private message notification when someone answers that thread.

After checking the code the only thing I think could be causing this is an edited template setting the 'subscriptionmethod' input.

Which template specifically?

According to your first post, I would guess it would be the _editpost_ template.