If you're watching a card, then in the footer of relative inclusions on that card you should see something like "watching |Parent| — unwatch".
(It wouldn't make sense to just have "watching |Parent|" and have it link to the parent card, because that will often simply reload the page, which would be confusing.)
As described this card is just wrong now, but the general issue remains. Maybe the menu for relative inclusions (formatted ones anyway, I think that's implicit here - we don't send an email if you edit a card a+b that's included on c do we? pretty arcane anyway...) just shouldn't even show "follow/unfollow" ? --John
fix watch link where watching is inherited+discussed in support tickets
fix watch link where watching is inherited+relevant user stories