Because of certain reasons, I'm sometimes tied to an extremely slow internet connection. What I realized with this, is that certain sites (for example, any subdomain of blog.hu) works in a way that needs a certain part of the site be loaded before comments are loaded too. I assume it's because of an AJAX operation, as the comments themselves are not visible within the HTML file.
In contrast, forum engines, such as vBulletin are often free from AJAX, meaning that when a thread's HTML is loaded, every comment in it are "hardcoded", meaning that even if the "fancy parts" (CSS, images and so on) are not loaded, I can already read the comments.
My needs are very special though, so I'm interested - is there any general UX advantage of any of these?