Well i am pretty new but from what i read in help files alignment can change based on player rp, but such change comes with some painfull cost of abilities, not to mention being shunned by those you turned away from.
was it not the case of Drizzt? They want to be drizzt, let them do that, they will just have to deal with their old friends who will want to impale them more than any other, plus the gods who shun them plus the skills that are gone, plus the fact that elf players will still not take them in as one of them. . .

And as a pretty new player i can say that the rp in this game is the best i seen anywhere, including the most popular ones.
I tried to call in some players from two rpg muds i used to play before (only to not feel like the easiest kill around :/ ) They came, they tried, they screamed and ran away with lame excuses.. one of them had the specific same problem as this.. in other muds suposedly same races have different history, allowing dark elf to be grey or dark.

Not all games are for everyone, and you need an iron gut to start playing this one. So someone who can't read the history of each race and the history of this world before creating a good dark elf won't stay in this game unless it transforms to be the one he is used to...
And frankly, i think CF is great as it is.