@retipster Zapier (or IFTTT) brings to mind our "Rewards" logic in NodeBB. It's rather rudimentary for now, but it could work with some tweaks?
ACP > Extend > Rewards
We could, for example, update the list of actions to include a "send an email" action, with customizable text.
That said, the triggers themselves look like they're coming from outside of NodeBB, right? That does complicate things.
The traditional approach here would be a custom integration with the NodeBB Write API, so you can do things like add users to groups, etc.
This requires a developer, though.