You are using Case Merge Premium and noticed that a comment from the child case was copied twice onto the parent case after a merge operation.
During a merge operation, Case Merge Premium will copy case comments (along with other child records) from the Child Case(s) onto the chosen Parent Case. Additionally, the application provides a configuration option called Duplicate Case Descriptions, which determines if the Description associated with the Child Case(s) will be copied.
As the first step in troubleshooting this, please compare the content of the duplicate comments. If one of them includes the text "Description merged from case#", this mean that the Description was merged as a comment due to the configuration of the above-mentioned setting.
If you wish to adjust the fashion in which case descriptions from the Child Case(s) are merged, please visit the Case Merge Premium Settings page.
If both comments are exactly the same and do not make mention of "Description merged from case#", please open a case with us by sending an email to email@example.com.