Ed Hansberry & Bruce Cannon - I agree - it would be neat for the planner notifications to function more like teams conversations. However, I do strongly feel they deserve to be obviously tied to individual cards to keep the conversation relevant to the reason it exists (and so you can refer and find it easily in the future w/in the plan).... pretty close to how "tab conversations" work. I'm not sure I'd agree that email should disappear entirely, though I do think individuals should be able to choose settings for notifications around planner cards quite the same way they can choose their own personal options for teams conversations.
Also... seems like they're headed in that direction still. I just dug up the specific https://planner.uservoice.com/forums/330525-microsoft-planner-feedback-forum/suggestions/11444235-email-notifications-and-alert-optionsand saw this:
Based off the feedback we’ve received so far, we have plans to address the following notification asks in the future:
1. Additional notification settings so you can choose how to receive your notifications (email, mobile push, etc.)
2. The ability to follow a task or plan and receive notifications when they change
3. Notifications when you are @mentioned in a task
4. Notifications within Teams