Comment 3 for bug 1652100

I've located the change that is most likely the culprit:

https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/14529#src/display/sp-canvas.cpp

Look at lines 1036 in the diff. Commenting out 'items->remove(item);' increases the speed of trunk an awful lot. It brings the de-selection time down to the selection time, which is about right.