I still am not running 3.5, and therefore cannot vouch for it definitely working. It SHOULD work, and people have told me they were able to get this hack to work via 3.5 *without* using plugins, but that's as far as I know.

The last post in thread URL produced (lastpostinthreadXXX.html) simply 301 redirects to the appropriate threadXXX.html page. It doesn't create a duplicate of the thread. This is proper SEO convention. Having the # appending a URL does not create a new URL as does a query string. The search enginges understand it to be a reference to a particular area of the page.

The forum jump is entirely irrelevant because a jumpbox is a form, and search engines cannot fill out or submit forms. However, it would be nice to hack for standardization alone. However, the benefits don't really outweigh the need to php hack the darn thing.