Some discussion boards (fatwallet is a notable example) permit the creation of a "quick summary" post immediately below the OP. This proves useful for summarizing the content of lengthy threads without imposing the full burden on anyone in particular.

The "quick summary" could be edited by anyone, as it is at fatwallet, or by the OP, mods, or some combination.

Does the BB software support such a thing?

See an example here: http://www.fatwallet.com/t/52/711457/