May 2019 Update: You now have Custom Subscription Themes
Now you can limit the types of notifications you receive for any problem and request retrieval so that they are specific to merge, reopen, and / or close events.

This should allow additional control over the number of letters received.
Update July 2017: Now you can declare the owner of the code in the GitHub repository.
Any request for access to a file managed by the specified owner of the code initiates a notification to this person.
See “ Automatically notifying the repo owner after updating the retrieval request ”
2015: Yes, for example, for a specific problem in the project ( problem 2595 ), you can register by clicking the "Subscribe" button on the right side of the page (from 2015).
After clicking, it will appear as "Unsubscribe" (if you do not want more notifications, you can click on it)

Thus, you do not need to watch all the repos, you can only subscribe to specific questions.
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