If you go into the comments on the blog post you see the way to instigate change, simply add hot water. The thing is, it is true. Like the saying goes "Know someone for 50 years, hold them over the volcano one day. On that day you will meet the man" The fifty years aren't needed, you just need to push them to the very edge and see how they react.
So in short, if you want the Characters in your game to change, you need to push them. More than that, you need to grab them by the throat and hold them directly over the mouth of the volcano. Make them stare death in the eye and see who blinks, see who spits in Death's eye, and then take them off that edge and see how they start to act having been confronted with who they are. Then, when they've started to readjust, you push them again. Maybe not to the edge again, but you do push them, see how they react. Those reactions will teach the player and you about the character, and as the situation pushes the character the character will have to change to be able to push back.
The trick to this is to hit them where they're not expecting it. Confronting a fighter with a fight generally isn't going to count as pushing them, afterall the character was made for that. A bread and butter fight for that character will not instigate change, it will instigate mechanics. So for the fighter you need to set things up special Hostage situation, something more than just them on the line, something they care about. At the same time, that bread and butter fight could be all you need for a pacifist character.
In general though there is no common way to push people. You need to make the situation desperate at times, challenging at others. Non-standard win scenarios at times, and a bit more normal at others. You keep pushing though, and the characters will keep changing to face what is pushing them. That change helps bring about depth, even in characters who are already fairly deep.
Have fun, and Happy Gaming!