I had installed FV Gravatar Cache Plugin by Foliovision on my website because many posts on my website have very high comments.
So I tried out this plugin on my website and tested a post with 1134 comments on a single WordPress post. I tested this out with Pingdom Full Page Test (FPT) to check out the improvement in post loading.
Results are as follows:
As you can see from the screenshots above, the total number of requests on the post before FV Gravatar cache plugin was 569 out of which 345 were requests made to Gravatar servers.
After the plugin was installed, the total number of requests reduced from 569 to 239.
Also the page size reduced from 2.1 mb to 1.5 mb.