It is like this being that emails are sent then the feature has to be working because nothing is going to cause an email to be sent to one person and not another that has signed up for notification. The only reason notification can not work is either your server is not setup for php mail or your not subscribed. We know php mail is working as some users are getting emails.
Not sure what you mean upload to a personal gallery and copy to that gallery making something work.
There are several different notifications in the program.
1. There are admin notifications where the admin can be notified of every photo or comment on the system.
2. There are category notifications which means that if you subscribe to a category you will be notified when there is a new photo uploaded to that category
3. There are photo notification where you request to be notified of when someone comments on a specific photo.
These are all long standing coding so we know it works I get notifications on my site all the time. If you want anymore help you would actually need to post a url and test login here and we can try doing some testing.