If a user has a follow-up comment in edit mode and also edits another field on the artifact, they are presented with 2 submit buttons - one fo the follow-up comment and one for the overall artifact change. Clicking on the submit button for the overall artifact saves just the change to the artifact field and does not save the change made to the follow-up comment. There is no warning that clicking the overall submit button without first clicking the follow-up comment-specifc submit button will cause your edits to the follow-up comment to be lost.
We would expect that the main artifact Submit button would save changes to all artifact changes, including the follow-up comment edit.