I am going to implement a comment system on a website and I'm going to implement Gravatar as user's avatars. Since the form for posting comments doesn't have a field for uploading an image, nor does the website have an option to even register your account (you only post comments by providing your name and email), I am worried that some people might be confused as to how or why a custom image appears next to some comments and others are generic.
I haven't been able to find any relevant answers to this question, but I also never saw any other Gravatar using websites explicitly noting they use Gravatar. So I guess my question is why I never saw that?
I would like to put just a tiny note, like a disclaimer, below the comment form that would explain that the image next to your comment is your Gravatar, with a link to Gravatar's website.