[Docs] Document behavior of Copy/Clone Comments feature

[zihanKuang]

Description:
There is currently missing documentation regarding the Copy/Clone Comments feature. This issue should address the following questions to complete the documentation:

• Will copying/cloning a comment trigger new email notifications to users?
• Are users’ prior notification mute settings preserved in the copied comment?
• If the original comment is resolved, does that affect the cloned/copied version?

[zihanKuang]

This issue is closed as it was resolved by #531