This plugin will apply the comment author name to each Gravatar's Alt text and Title tag in the comments section of your posts, it also applies t …
This simple, lightweight plugin solves one particular issue. WordPress doesn’t include any alt text or a title tag when using Gravatars. This addresses that by using the comment author name for each of your comment’s Gravatars, and for any other Gravatar usage it should use the authors display name.
So if you create a post it will use your name for your Gravatars Alt text and Title tag and then for the comments it will use the commenters name for their Gravatars Alt text and Title tags.
With this plugin you can squash those pesky warnings given by SEO reporting tools that look for missing alt text and title tags.
Or you can just copy the function and drop it into your functions.php file, if not wanting to use yet another plugin.