The trick with the selections tools in 2.10 is that you have to strike Enter (or double click inside) to "commit" them. In you case this is a good thing because you can edit the node even after you have closed the selection.
Check if you have a grid defined/enabled (View>Snap to grid and Image>Configure grid).
Btw, even with the scissors you can add control points to fix inaccuracies.
Check if you have a grid defined/enabled (View>Snap to grid and Image>Configure grid).
Btw, even with the scissors you can add control points to fix inaccuracies.