Bug 339573 Splitting the shared area with a part doesn't remove stale placeholders
The current code only looks for the addition of an MPlaceholder in the shared area as the hint to remove locals. When you split the area the element that gets added is the new MPartSashContainer...
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
Object w = createGui(added);
					if (w instanceof Control && !(w instanceof Shell)) {
						fixZOrder(added);
						((Control) w).getShell().layout(
								new Control[] { (Control) w }, SWT.DEFER);
					}
				} else {
					if (renderer != null)
						renderer.childRendered(changedElement, added);
				}
				
				
				
				int newLocation = modelService.getElementLocation(added);
				if (added instanceof MPlaceholder
						&& (newLocation == EModelService.IN_SHARED_AREA || newLocation == EModelService.OUTSIDE_PERSPECTIVE)) {
					MWindow topWin = modelService.getTopLevelWindowFor(added);
					MPlaceholder addedPH = (MPlaceholder) added;
					List<MPlaceholder> phList = modelService.findElements(
							topWin, null, MPlaceholder.class, null);
					for (MPlaceholder ph : phList) {
						if (ph == addedPH)
							continue; 
						if (ph.getRef() == addedPH.getRef())
							ph.getParent().getChildren().remove(ph);
					}
				}
			} else if (UIEvents.EventTypes.REMOVE.equals(eventType)) {
				Activator.trace(Policy.DEBUG_RENDERER, "Child Removed", null); 
				MUIElement removed = (MUIElement) event