To anyone stumbling into this thread wondering how the subscriptions are stored in the database, it has been updated.
To find out what users are subscribed to a topic or thread you need to look for the _bbp_subscription meta_key in the wp_postmeta table. There is one for each user subscribed where meta_value is the ID of the user subscribed.
So for example, to know how many users are subscribed to a forum or topic, just count the number of _bpp_subscription metadata present with post_id of the specific forum or topic
@zee300 can you confirm you are using buddypress?
I’ve noticed exactly the same thing on my install and have reported it on BuddyPress forums.
