You can view issues you've commented on by using the following search string in the search box (prepopulated URL):
is:issue commenter:@me To show only open issues, add the is:open qualifier (prepopulated URL):
is:issue commenter:@me is:open The search can also be adapted for any user by replacing @me with their GitHub username. Do not include the @ symbol in this case.
For example, for the username defunkt/@defunkt use (prepopulated URL):
is:issue commenter:defunkt 