I wouldn't say he is going to not do anything out of the norm, rather the player will either learn to be a better player (which back in the day, before XP required to lvl was lowered, and in the hayday of 4k/hr parties you had to play at a higher level (which is a good thing)), or in the case of exploring, they'll be safer and more aware of their surroundings (which, again is a good thing. Hey don't aggro those 3 mobs in Promies! (Back when mobs raped! before the nerf)).
Simply a raise sickness is not enough to deter. They'll continiously just throw themselves at the mob not fearing any repercussions. With a growth penalty they aren't. They will try a few things, take a step back and analyze the situation. That is in the best benefit of everyone as it improves the quality of players. No one likes to play with noobs. Teaching newbs however, is something I enjoyed doing.
I leveled beastmaster in FFXI to 75, mostly solo. I died so many times it was ridiculous, and each of those times I got half to full exp penalty. After awhile, you get to the point where you get tired of being pummeled for every mistake. And beastmaster, one mistake will kill you dead. It may not even be anything you can do-the random number generator behind charm may just ***** you twice, and you are dead. I died like 7 times learning on a mob no one ever experiences on (magic pots, you have to learn spacing to avoid ga spells and deal with gravity when you may not be able to remove it)
Another example was in aht urghan. I had flagged a quest for the caederva mire map. I didn't read on the wiki, and had forgotten the text (there is no real quest log) i saw a ??? outside in the thickets, and clicked it. A NM spawned and beat me to death. I lost 2.8k from that and learned to religiously read the wiki over anything suspicious.
i do not want that experience in a game ever again. I want to be free to make mistakes on occasion without having to lose 30 minutes to an hour progress. If the game is fun, I will want to be a good player. Sometimes you need to die to experiment-i shouldn't have to feel horrid because my party yelled at me and disbanded because i killed them twice while learning how to main heal in valkurm dunes.
When they did the alexander fight in toau, they removed the exp penalty. It was a wise move because people would go 0-10 on it without being stupid. They read the wiki, they followed the strategy as religiously as they could, and they still wiped. Sometimes a penalty is just that, a penalty. You can do everything right, and still fail, and the exp penalty makes the failure sting.
I'm not saying remove failure, but there as to be some kind of middle ground between no consequences, and look the **** up out of everything on the wiki and totally understand everything so you go 1/3 instead of 0/15 and delevel.