I'm baffled by your suggestion that this is how discord does it, because I have used discord for a while and never seen threads (I use the web app and not the mobile app though). Am I missing something like this?
In Discord you can certainly reply to messages, but that basically just references them. Messages all appear top-level in their channels. There is no "side chat" that will contain the threaded conversations.
Again, unless I'm missing something due to using the web app and maybe having threads disabled in my settings.
Mattermost is very different in how it handles this. I haven't used Slack in a while, but IIRC it's much more similar to slack
This has grown into a longer series of misunderstandings than seems necessary. :P
Yes, Discord's behavior with regards to the initial creation of threads is not the same, if I understand you right. To create a thread, one has to explicitly click a New Thread button, OR Discord will prompt you after 2-3 replies in a row to create a thread for that message chain. After that, the thread will show up under the top-level channel, and you can open it up in a sidebar. *
What I meant when I said this is how Discord does it was with regards to how messages are shared - or not, as it is - between the top-level channel and the thread. As I said, I misunderstood earlier comments regarding how this works on other platforms. I really ought to just download Mattermost and check it out :P
* If you're not just talking about specific thread behavior, and indeed have never seen threads at all, you're not alone. They're not very commonly used on Discord, probably because it's not easy to discover them. They're also a relatively new feature.
I believe Discord servers can disable "threads", which maybe what you've seen.
If you right click on a message you can choose "create thread" and it will do this thing (which I personally hate). You can do this on the official Python server for example.
In Discord you can certainly reply to messages, but that basically just references them. Messages all appear top-level in their channels. There is no "side chat" that will contain the threaded conversations.
Again, unless I'm missing something due to using the web app and maybe having threads disabled in my settings.
Mattermost is very different in how it handles this. I haven't used Slack in a while, but IIRC it's much more similar to slack