Rigged character animation is messed up if there's changes in vertex?

I used to use weight paint in order to rig and animate my characters. When you have a finished character and then move some vertex, the animation will be affected because I think some vertex will be gone, added or moved to another position.

How do blender handle this kind for situations?

I was checking th mancandy

I wonder what kind of method the author used in order to rig his character.

Any suggestions?

I want videos of Rigging and Skinning in blender 2.5. And python Scripts for Rigging. Pls help me out