At least in my web browser, Firefox, the individual posts in a thread are missing any horizontal border to divide the posts from one another. Makes it hard to read.
I have noticed that as well. I'll take a look to see if it can be edited in the styles admin.
edit: nope, that cannot be edited in the styles admin, looks like it will take a manual edit to the template or css files which will be overwritten on the next update as well.
edit#2: I added a yellow line to divide the posts in the css file settings, let me know if this works OK.