Comment on SEO Super Comments WordPress Plugin by Mark.
The Gravatar functionality is a nice from a user experience standpoint and I think Gravatars will only get more popular as the web expands, not less. This coupled with the fact, Gravatar plugins are pretty light in terms of development, yet Gravatars are used on every WP website. Plugins done right are marketing tools as well as useful.
The Child themes you can do a lot with for reasons mentioned. I have many customizations I forget about. You can have Stallion child theme developers which is good idea, help get the world out.