Please upgrade to 2.2 here.
The 2.0 and 2.1 branches are no longer being updated.
[EMailSubscribe Addon] User receives email when you EDIT an existing discussion
I found this to be a major issue with the EMailSubscribe-Plugin: when you edit an existing discussion of a category users have subscribed to, they will receive an email just as if the discussion was newly added.
This is very confusing and should be fixed.