This is very close to what we’ve been struggling with too.

But in practice, a lot of things never even become “tasks” — they stay in threads.

We tried reactions as status (✅ = done, etc.)

It works a bit, but breaks quickly with many active discussions.

The main issue for us is earlier:
how to track which threads actually need action vs just being informational.

We started thinking about threads more like an inbox (needs reply / waiting / resolved), and even built a small tool around this idea:
https://www.threaddesk.work/

Feels like there’s a gap before tasks — at the thread level.

We recently created a plugin during one of our Hackathons that acts as a To-Do/Reminder system. It's in it's early phases, and there are features being actively added by the community as we speak.

The basics are there: Create, View and Complete Tasks.

Some plans we are thinking about: Sending a To-Do to someone else, UX improvements to make it easier to use common tasks. In the future, we can see this being integrated with our Workflow system, allowing events in Mattermost to create a To-do for users automatically (say, when an incident is logged, create a Todo task for users on call to "Perform a Post-Mortem").

The plugin is not yet available in our Marketplace, but we plan to release it this quarter (by end of March).

If you'd like to check it out, or make some suggestions (log an issue on the repo) - you can find the plugin and development progressing here: https://github.com/mattermost/mattermost-plugin-todo

Ryver has this feature.
I have just moved from ryver to mattermost & I miss the simple task management feature in Ryver!

yes I used an integration module in slack and also I used basecamp and trello for this things, but implementing these little things like Task creation, Task assigning would be great in a team environment.