Apps documentation
Issue SYNC for Jira Cloud
Issue SYNC for Jira Cloud
Introduction
Architecture & Versions
Development
Last updated Nov 1, 2020

Depending on How to configure synchronization configuration comments can be synchronized:

None Comments may NOT be synchronized at all. This is default option. -
All All comments may be synchronized using built-in Comments tab.

When do you know that comment is synchronized?

That info will be added to each comment:

You may also check Synchronization History