Through testing I have identified and ended up sticking to old version of CommentLuv plugin - 2.8.31 in order for it to work.
Some details on blog: http://www.howtospoter.com
I use nginx server with full core caching
Use object caching plugin
Use CDN for offloading static content
Not sure if anyone else run into this issue or not but I do know that plugin was re-written since 2.9.1 and starting from that version - it fails to work - just clocks on my blog without being able to pull last commenter post. I tried enabling "caching" compatibility - no luck.
2.8.31 work with no caching enabled under commentluv options