In chrome, I right clicked on the body text and hit "inspect element". That brings up element inspector with the relevant element highlighted. The highlighted div had the id "comments". Hovering over that element in the inspector pane shows you the dimensions of the div in blue and the padding in green in the main windows. This makes it pretty easy to see that the comments div is covering everything else.

The css for #comments in the inspector pane doesn't specify dimensions for the div, so it should be the size of its child elements. None of the child elements overlap the body text or sidebar, so something else is causing the parent div to cover those elements.

The div directly before #comments is the sidebar, and clicking on it in the inspector pane shows the css floating it.

I then just added a clear: both to #comments using the inspector and it fixed the problem in the main window. You can add css to an element in the inspector in chrome by hitting the "+" in the right-hand pane (there are other ways, but that's probably the easiest).