it is easy to start just past TDC, because you are kicking it over after the compression stroke/spark has happened, as you push down on the kickstarter it is only drawing fuel/air in, then the next stroke it goes to the compression stroke, before it is about to fire
so kicking the engine over past TDC, has given it momentum getting it spinning over and it wont be sparking while you are kicking
if you just kick it from anywhere, if it is just about to fire and does, it can give you a big kickback
the minimum damage it does is a huge shock through your kickstart gears
usually the weakest point is the Idler gear in between the kickstart and clutch gears