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.
My team is currently working on redesigning email threads. The redesign will show newer emails at the top of the thread to match the chronology of the timeline.
Feel free to send me a direct message if you are interested in having your portal added to the Beta when the time comes!