Symptom:
If the Other E-mail Addresses field is used for an Email action, the names listed in that field get added to "TO" field twice.

Conditions:
Create an Email Action filling in Action Name, Owner, Subject and Message.  Using the ellipse button (...) for the TO field, select a user with an email address configured from the "Scheduler E-mail Addresses" section and click OK. There is one email address in the To field. Click OK to exit the dialog.  Go back into the Email action to the "TO" field.  Add an email address in the "Other E-mail Addresses" section and click OK. The "To" field contains 2 email addresses.  Click OK to exit the dialog.  Go back into the Email Action again.  Now there are 3 email addresses: 
2 for the "Other E-mail addresses" name and one for the "Scheduler E-mail addresses" name. 

This is a visual issue only.  Functionality works properly.  There are not duplicate emails sent.