S2 people: how do you want the URL to enter flat mode exposed to you? It will not be the default, and I'm not going to argue with people who might want that. Its purpose is for when people really want it (usually community maintainers or people browsing popular communities... "oh yeah, I left off on page 18 of 28!")
This won't be done for S1, because my plan is to implement all the existing S1 BML views (talkread.bml, view/index.bml, etc) in terms of S2 styles that just look like the BML files, so we remove a lot of duplicated code.