Do I have to endorse a Canadian dollar check being deposited into a
Canadian bank account?

No you dont.

I tend to believe such short comments, but being rather of a different
opinion  (why do they space for an endorsement?) think that applies if
you are depositing a check that has been issued in your name to your
own account.  If you are depositing it to an account in someone else's
name, the check needs to be endorsed to signify that you  - the
beneficiary of the check -  had had possession of the check and
personally released it for deposit in someone else's account.

Well, maybe the laws or modern practices in Canada are different.
I am sure someone can clarify the matter.