`Reply as New Topic' is a pretty elegant solution, but has a huge failure point: the user. It might work with a technically minded audience, but with Joe Bloggs, it's almost certainly not going to be used. The result will most likely be one massive thread that lurches on and off topic post-by-post, with the responsibility for forking it into new threads -- and replies to the OT `new thread' -- pushed onto the moderators/admins.