users don't get email when they get comments
 

hello,

users report that they don't get any email reporting a new comment on their picture. how can i fix that?

Have they selected to be notified when they uploaded the photo? If they have not elected to be notified they will not be.

How do we set the "receive email after new comment" to be CHECKED by default?

You would need to alter your upload photo template and change the html for the notify select box to have yes selected and not no.