Multi-selection via drag in filtered AlternatePluggableListMorphOfMany broken

[LinqLover]

Steps to reproduce: Bring up a message set with many items, type something to filter the list, and click-and-drag to select a range. Press enter to delete the filter.

Expected: Just the items that were visible during the filtering are selected.

Actual: Many more items are selected. In some situations, some items are already (de)selected unintentionally while dragging beyond the "frontMatching/substringMatching" border.