One thing that we wanted to do was to create a design that was more modern and a bit more familiar to the average Slack/Discord user. I think zulip is great but can be a bit more overwhelming. We wanted to keep a familiar UX as much as possible while giving the benefits of a thread first experience.

Secondly we are a bit more opinionated in thread management. Our inbox is designed to get to an inbox zero state. We have things like !mention vs @mention which helps with urgent vs non urgent communication.