...you could make a case that the damage this rule does is worth the benefit it brings .. rather than plugging your ears and insisting that it doesn't cause any harm.
I will agree that, from a certain perspective, this rule could be considered to be "hurting Dwilight". There is definitely a lower character count on Dwilight than there could be if we lifted the rule. We could potentially see player densities as high as other islands if we did. And to be completely truthful, the lower player densities do have a negative effect on the island.
For myself, though, I think that the disadvantages of the lower player density are well worth what we get in return. From a player standpoint you get the knowledge that each character is a unique character with their individual motivations. You don't get the zombies, alts, and second-character-sheeple which drive those higher densities. You generally don't have those secret ties between realms that are defined and cast in concrete due to second characters in the other realm. (Yes, you can still have secret alliances. But secret alliances worked out between multiple players are much, much different than secret alliances that exist because John Doe plays the power character that runs two different realms.) You don't get realms propped up by 5 of the 7 players in the realm bringing in a second character. (Although you still do get those people that start an advy, move him to their realm, and then use that advy as a proxy for their noble under the guise of "I'm Lord Kepler's messenger"...
)
The first is that everybody is a lord and so the feudal ladder has had rungs removed. Nobody has knights. This reduces the value of higher titles because there are so many to go around. When everybody is a Duke, Dukes ain't special.
I partially agree with this. We do have a lot of lords. But then again, a lot of players don't bother going for those higher offices simply because they don't want the hassle/responsibility. I have passed up multiple council positions and influential religious positions simply because I don't have the time, even on other islands with higher character densities. I would bet that almost every other player does the same thing. Dropping the one-character restrictions may slightly increase competition for positions on Dwilight a bit. But it would also drop competition on other islands as well, as people leave those islands to bring a second character to Dwilight.
So yes, I agree that there are some negative aspects to the one-character rule for Dwilight. But I think the positive aspects it brings to Dwilight more than compensate, resulting in a net positive. If you don't like the resulting lower player density, then there are plenty of other islands to choose from.