@Peter Kahoun - I never said anything about how much these SEO benefits are worth, just that they are beneficial features which other forum softwares don't have.

Whether a backlink is nofollow or not is irrelevant to whether it is beneficial to have SEO wise or not. Non nofollow links are better, but nofollow links still have SEO benefits as it exposes your site to more people and hence are more likely to be linked to in the future. It's an indirect SEO benefit.

Most other forum software do not include good on page SEO optomisation in their default theme, bbPress does.