Since ArcGIS 10.2.1, double-clicking a feature while editing vertices causes the layer to redraw resulting in latency. This was not the case in ArcGIS 10.0 SP5.
Dependent on the count and complexity of the layers, which are quite high for Utilities, this redraw results in a significant latency and makes a continuous working impossible.
This behavior is caused by a change in ArcGIS 10.2.1.
The original behavior can be restored by setting a registry parameter.
EditVerticesOpaque dword = 1