Order of Email Threads Should be Newest First
The chronology logic of the timeline is currently inconsistent. Generally, timeline items are displayed "newest first" which is great. However, within threads, you show oldest first.
Now it is true that Gmail has the same logic. But if you click on a thread in gmail, you are taken in a new environment, whereas in Hubspot you stay on the timeline. So it is easy to get confused about the chronology of things.