Why do I see duplicated Jira fields on the mappings?
Purpose
When you click Mappings in the Salesforce configuration page to map Jira fields with Salesforce fields, you may see a duplicate field option to choose from.
When checking for the duplicate field in the Custom field section, the same field shows up only once.
Answer
This happens in a team-managed project. These duplicate fields will not appear in the Custom Fields page.
The Jira administrator has to change the team-managed custom field name to differentiate the fields.