Ummm.... YES, there are great (potential) differences between non-Superuser and Superuser connections and their abilities. Apparently when your users were created, someone added superuser abilities to each one. That is almost certainly an error. You may have users which should have read-only ability others who should have read-write, and far fewer with superuser. Check the web pages for GRANTS as to what each user can have. If you have lots of users and don't want to assign each individually, then make a group role, give it the abilities you want, then assign your appropriate users to that group. Sounds like you need to read up on database security.
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Jay