Glad my findings helped someone :)
Best thing to do if you're unsure about making live changes is to use either Chrome, right click on the Disqus box and go to inspect element or Firefox and install the Firebug add-on to do a similar thing.
You can then change the values you've set as much as you like, to decide where you'd like it to be positioned. The changes you make this way are only applied to the current session your browser has, i.e. no one else will see you messing about. Once you've found the values you want to use just change them in your CSS.
The line you're looking for is:
Once highlighted, you'll see on the right the CSS changes we've made above.
I've had a play about, and I'm guessing you want it a bit more central?
I tried changing the margin-left to 130px which seemed about correct/central, although I can't vouch for this being the best way to "code" this as I'm only fumbling around to be honest!
Hope this helps!
Fun site btw!