...this unfortunately makes the feature almost unusable for any sort of modern automation-heavy music. The only way to ensure preservation of endpoints is by creating a selection, select-all (Ctrl-A), and Ctrl-Dragging items to duplicate -- but this only works on automation attached to items!
Every other DAW has an 'area selection' tool with which you can copy/duplicate/delete precisely whatever you select. If Reaper's sticking with Time Selection, this needs to work properly or it's unusable.
Thanks! Favourite DAW on the planet, and will stay that way with bugs getting squashed.