Comb structures are widely used in micro-electromechanical systems as basic components of electrostatic actuators, capacitive sensors, resonators and energy harvesters. Typically, they are operated with a large overlap of the comb fingers, in the linear region. Here we study the behavior of comb-drive actuators during the displacement along the axis of the fingers in the unconventional regime where the fingers are slightly overlapping (around the width d of the fingers), which has recently gained attention in the MEMS community. In the intermediate region where the overlap approaches zero, fringing electric fields induce a non-linear variation of the capacitance, yielding a significant electrostatic force between the combs even without finger overlap with a maximum gradient occurring in this region. The comb capacitance variation with overlap was calculated using analytical and FEM modeling and confirmed with experimental results. We explored the implications of this condition in both static and dynamic modes, highlighting the effect of spring softening arising from the second derivative of the capacitance. These findings introduce new operational possibilities for actuators and sensors and substantial tunability in frequency for resonators.