ValhallasAshes: Don't think of it like a "penalty". It's choice/consequence. Those choices build up points in either direction and could be used as skill checks for certain actions. You can go all light side, dark side or even grey. But there's also enough wiggle room where you don't have to get every decision right or even every decision in the same light/dark direction. I've played KOTOR and KOTOR2 and even KOTOR2 had plenty of wiggle room.

The problem in KOTOR2 was that there was a lot more ambiguity in the dialogues that made the "right" or "wrong" choices when interacting with certain characters a lot more difficult. How far do you go down a certain dialogue path. Where do you draw the line and say "lets not explore this particular conversation topic any further".

KOTOR 1 was a lot more straight forward in that regard. Where as KOTOR2 was a lot more like navigating the dialogue options in Wing Commander IV during the congressional assembly scene, where even what you would think would be the obvious choice, could be flipped to your detriment so easily. Mass Effect had some similar outcomes in some scenarios, but the wheel organization made it a lot easier to know which direction your choice would reflect before you made it.

But no, whether you're playing KOTOR 1 or 2, you force leaning won't necessarily "punish" you, but it will have a significant impact with what options/choices are available to you at certain points in the story.