We actually moved from Mattermost to Zulip. Mattermost and Slack work fine for highly specific project teams but when used in an Enterprise for the day to day operation the poor threading solutions in both become a drag. Especially the ability to react outside of a thread created chaos for us.

We've switched to Zulip which has a real nice messaging threading model. For us it was really a productivity saver and I really recommend anyone to try Zulip!

Mattermost team here, thanks for the mention!

Yeah, a lot of enterprises are using Mattermost these days. Uber left Slack and HipChat to use Mattermost for company-wide deployment: http://www.businessinsider.com/uber-ditches-hipchat-slack-to...