Yes. I downloaded an installer from a Google Code archive and was able to break the synchronization within a few seconds (just like I remembered). The views available were Book View (F9), Split View (F10), and Code View (F11). It was actually split horizontally.
Attached is a screenshot of Sigil 0.5.3's Split View in action (QStackedWidget with a horizontal splitter). Split View disappeared sometime before the official 0.6.0 release (which represented a considerable overhaul of Sigil at the time). It was deemed much easier to ditch than maintain. Seems we weren't the first Sigil devs to ditch popular, but terribly problematic, inherited boat-anchor features.
