So I am one of the new profession in RM, the Necroposter, lol.
My take on elves, is -20 is appropriate, and frankly there should be more penalties. I would say like -90% to experience gained for one.
But for gameplay in the past I actually did a -20% experience for elves. I don't think enough is done to cover the negative aspects of elves, always glorifying their good ones.
I think a huge factor in elves, is that most non-elves would dislike elves, and rightfully so. They're arrogant, self-centered, closed-minded, condescending, see things of other races as trivial, and extremely racist. Time would almost be meaningless to them. You know how you feel when you're waiting on someone who is always late to go to the movies? Imagine that kinda thing x100 with an elf
I don't see them as chaotic good as d&d would put them, more of CN, only being CG to other elves. Some would be very militant, and have a skewed morality in comparison to other races. I see an elf being capable of killing off a human to save a tree (that there's a whole forest full of.) I personally see that as an evil act, but in the mind of an elf, that wouldn't. And when other humans (or even dwarves, halflings) find out a person is dead over a common tree?
Now ofcourse there are individual elves that would not be exactly like that, just as there are evil humans, dwarves, etc