Copied this from previous post where no solution was given. I am having same problem and DO NOT want to get emails every time someone else comments on the same activity I have commented on. Strava: please fix your problem with this!!!
Every time I comment on a notable activity (such as a race) of another Strava user, my email inbox get flooded with comments from other users on the same activity, most of whom I don't know and completely uninterested in their comments. Most of these comments are simple congratulations.
Is there any way to stop that? I have already unchecked a corresponding option for a push notification, but I still get emails. For example, after yesterday's race, in which I also participated, I received at least 20 such emails about someone who I don't know commenting on another person's race.