Hi, this week I changed the SPPoint selection to use Inkscape's normal selection mechanics instead of the control-point-selection.cpp. This has the advantage that selecting points and connectors at the same time is not quite as bad a hack as it would be otherwise.
Doing this I introduced a new signal for selection/deselection in SPObject.
I also changed the UI a lot to make it possible to reconnect connectors. SPPoints are now created by shift-clicking into the document while the selection is empty. If the selection is not empty, shift-click toggles the selection of the object under the cursor. Control-click should work as expected with groups. Connectors are terminated by clicking on the end point or somewhere in empty space (in which case a new SPPoint will be created on the clicked location).
Sometimes stray points still appear because I have not yet found out how to delete SPPoints without crashing Inkscape. I am working on that.
Connector deletion appears to work now. SPPoint deletion still has its issues. After deleting a SPPoint, Inkscape crashes with ominous memory corruption errors. I was unable to find the cause of that so far. I will push a commit later that allows easy reproduction of this.
Sebastian