I've spent a lot of time thinking about all the possible solutions to the problems associated with chat rooms. The issue that it's hard to talk about multiple things at the same time in a channel is common to Slack, IRC, Jabber, and just about everything else. So have spent a long time designing and building a better solution to those problems.

It's hard to talk about Slack's threading solution without also talking about what I think is the best way to solve that problem.

Zulip is great. After using it for a while, I no longer want to use anything else.

The light-weight topics make a lot of sense. You can quickly discuss a topic and then forget about it.

With Slack, you'll need to create a new channel, invite people into it, it's just much more overhead so you end up discussing in the main channel.

A huge issue with Slack, for me, is catching up with busy channels. You have to read all of it since you miss discussions on topics you're interested in. Zulip has a great solution to this issue.

I'm also impressed with how high-quality it is. They even have Nagios checks and everything. It has many features you miss in other products like Rocket Chat (full text search. administrative tools, ...).

Edit: relevant comment from another thread. https://news.ycombinator.com/item?id=10281065

I found it tasteful and relevant and didn't feel spammy because of the discussion contrasting a feature many people want that Slack doesn't have (or didn't until today and may not still be exactly what we want).

Zulip is an open source project with no way to purchase it from what the home page shows, so doesn't seem like that big a deal to me.

It's 100% open source.

Zulip used to be a company until they got bought by Dropbox (who were after the team, not the product).

Dropbox decided to open source Zulip and tabbott invested and continues to invest lots of (what I assume to be his free) time to make it happen.

The community around Zulip is extremely active and there's lots of high-quality development happening.

https://github.com/zulip/zulip

Isn't TFA an actual marketing post from Slack for their new feature?