They position the thread id at the beginning of the URL rather then at the end.
I have the understanding that Google and other search engines offer a weighting based on where terms are found within a URL, with a priority given for terms at the end of the URL. In other words if all things are equal and you see the following two URLs, the IPB listing would be ranked higher in Google. If that is the case, perhaps a consideration of adjusting the URLs is in order. Yes it would be painful in several regards, but if it results in any SEO improvement, then perhaps it is worthwhile.
IPBoards URL http://www.terafans.com/topic/8879-tera-around-the-world-scapes
XF URL would be http://www.terafans.com/topic/tera-around-the-world-scapes.8879