Indenting categories

[ZiNgA BuRgA]

It's just HTML and maybe CSS.
You're using XThreads because you know them, right?  Because if you aren't familiar with either, you shouldn't be using XThreads.

If so, just go onto a edit post page and copy+paste the HTML into your editpost and newthread templates, then tweak it to your liking.
There are a few other things, but if you can do the above, the rest should be trivial.