Publish btn should be active all time - if user is stucked he/she can click on publish btn to highlight fields which is not filled correctly. What is problem here is unconsistency - at the start btn is disabled and after two interactions publish is enabled.

Look this feature is great for a lot of comments and activities over time. While you scrolling it improves your orientation in time because your eyes is focused primarily on the left side and change focus on the right for orientation is overwhelming. Time on the left is time of group of activities and time on the right is specific time of each activity and you can view its detail on hover.
e.g.
https://report.bistudio.com/issues/DZG-85
https://report.bistudio.com/issues/ARGF-222

@dragino as guest testing