This is more a curiosity question than anything else. We are starting to use Planner, and comment on tasks frequently. I read in one of the recent posts that task comments are stored in an online mailbox. But we havent set up anything with Exchange Online, haven’t touched it at all.
Does this mean we have hidden online mailboxes that we can’t access that is storing all these comments? What happens when we eventually enable EXO?
Planner relies on Office 365 Groups and it's possible to create Office 365 Groups without having EXO service in use...so to my knowledge, what you are saying is just correct...behind the scenes everything you need is being provisioned so Planner comments also work. Obviously, in this scenario you will not be able to access the "hidden" mailbox to check thos comments