litefeel

Comments Avatar Lazyload at server side load replace the src property of img tag. It is relly lazyload. It was successfully checked by W3C. 
It is only lazyload comments avatar.
Related Links:
<ul>
<li><a href="https://www.litefeel.com/comments-avatar-lazyload/" title="Comments Avatar Lazyload Plugin for WordPress" rel="nofollow ugc">Plugin Homepage</a></li>
<li><a href="https://www.litefeel.com/" title="Author For Comments Avatar Lazyload Plugin" rel="nofollow ugc">Author Homepage</a></li>
<li><a href="https://github.com/lite3/comments-avatar-lazyload" title="On GitHub" rel="nofollow ugc">On GitHub</a></li>
</ul>

Comments Avatar Lazyload

Comments Avatar Lazyload at server side load replace the src property of img tag. It is relly lazyload. It was successfully checked by W3C.

Taylor Callsen

Automatically populates Alt and Title tags for images featured in posts and pages, pulling directly from the values set in the Media Library. This makes it easy to manage your image metadata centrally in one place (the Media Library). Plugin also supports the ability to override the Alt/Title tag Media Library values by placing an Alt/Title tag directly on the attachment in the WordPress WYSIWYG Editor.
Tag population only occurs when viewing the post or page, and does not occur in the WYSIWYG editor.

Auto-populate Image ALT Tags from Media Library

Automatically populates Alt and Title tags for images using the values set in the Media Library.

Comments Avatar Lazyload vs Auto-populate Image ALT Tags from Media Library