You do open the thread, displaying all entries at once? Do you open the thread in the linear or in the nested view?
It's only when I open the full thread displaying all posts in the thread. So when I click "open in thread" either on the original post or any replies the browser loading circle spins and nothing else happens, it just sits there for like 15-20 seconds before then instantly loading the page but I think most people would have given up waiting before that.
I can have it set to Linear or Hierarchical and it seems to be about the same loading time.
Like I said the thread is mainly just text, no large jpg or gifs or any links.