Bug 125272 [Viewers] AbstractTreeViewer needs remove(Object parentElement, Object[] childElements)
There is an add(Object parentElement, Object[] childElements) but no corresponding remove(). Without this method, if you have an element that appears under multiple parents, the only way to get model and viewer in sync after removing the element from just one of its parents is calling refresh().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if(treePath.getSegmentCount()==0) {
				return null;
			}
			Widget[] candidates = findItems(treePath.getLastSegment());
			for (int i = 0; i < candidates.length; i++) {
				Widget candidate = candidates[i];
				if(!(candidate instanceof Item)) {
					continue;
				}
				if(treePath.equals(getTreePathFromItem((Item) candidate), getComparer())) {
					return candidate;
				}
			}
			return null;
		}
		return findItem(elementOrTreePath);
	}
    /**
     * Recursively expands the subtree rooted at the given widget to the given
     * level.
     * <p>
     * </p>
     * Note that the default implementation of this method does not call <code>setRedraw</code>.
     * 
     * @param widget
     *           the widget
     * @param level
     *           non-negative level, or <code>ALL_LEVELS</code> to collapse
     *           all levels of the tree
     */