The problem is that the server has to serve the entire page each time.
Most of the other sites have gone to html blocks so that the blocks are queued in a cache and don’t have to be reserved.
This enabled you to set up proxies to serve up the cached html blocks enabling the server to boost it’s performance since it is only serving the new html blocks and not whole pages.
Currently the Index and Comments are all one continuous html block that can’t be cached effectively.
I should say also, with the use of html blocks, in most cases the blocks are served from the user’s local browser cache so the proxies don’t even get hit by the users.
We’ve been using a caching system for years.