[Michael Adams (mdawaffe)]

do you mean that “after upgrading and changing the permalink structure of a forum; the old permalinks does not redirect to the new one” ?

No, I just meant that with the current code, if you’ve somehow managed to change the slug, you’ve broken the old links. But, as you point out, bbPress knows how to move “sideways” across different kinds of permalinks.

WordPress allows you to change the slug and automatically redirects your old links to the new slug; it’s more clever than bbPress is at the moment