I am a frequent user of Yahoo! comments but I don't know how to change my profile picture. On the profile edit page you can change your nickname and above all that your default picture is shown but no option to change it. Am I missing something? How can I change that?
The ability to change ones profile picture went away when http://profiles.yahoo.com shut down in January, 2015. They've not introduced a new method to change your profile picture.
From Yahoo! help:
Update your Account picture
Yahoo Profile (profile.yahoo.com) no longer exists. But don't worry - your comments on various Yahoo properties didn't disappear! Most relevant settings are now in your account settings. We simply removed the ability to view public profiles and the “about me” and “my interests” sections, but you can still post comments on the various Yahoo properties and your Yahoo nickname and profile pic still exist.
Coming soon! - This feature may not be available on your account just yet.