[Opserty]

If you don't know HTML this probably won't make much sense but if you do:

You need to <!-- show threads --> comment, then go up a little from it and find the table headings the will be using the thead class. Add in and extra table cell on to the end (with the thead class and whatever text you need)

Then go to the threadbit class and find the last table cell (before the inlinemod checkboxes) and put in your table cell. Then you need to find the table cell where the thread name and starter are displayed. Look for the piece of code which holds the thread starters name. I think it is $thread['username'] but you will have to check the to be sure.

I think thats most it, sorry its not very accurate I don't have a working Copy of vBulletin handy.