Hi Andrew,
I am assuming that the reason why you used Dd versus D is because in the Vietnamese alphabet, there is another D with a bar in middle of the downstroke capitalized and a bar crossing the top of the downstroke in the uncapitalized "d".
If this is correct, then this is my understanding. The other Vietnamese D has always been converted to our D for lack of equivalence. There has never been another way to represent it. The Vietnamese just figure it out when needed. However, there is an informal convention that has been used among Vietnamese to represent the other D and d as Dd and dd accordingly. It was never recognized by any formal means, just a way that Vietnamese use for email or chat to distinguish these 2 different D's among themselves.
I would suggest that you ask for the correction otherwise, it would cause all kinds of confusion. An almost parallel to this problem was that the Vietnamese write their last name first and first name last. Shortly after 1975, many Vietnamese ran into troubles with many businesses, agencies, schools, banks, etc.. with this problem. They never liked their name being reversed but eventually they had no choice but complying the U.S. convention. Each time they ran into this problem, it was more difficult to explain and to correct the problem than just to reverse their name.
I hope this helps somehow.
Tony
QUOTE(andrew va thuy @ Oct 28 2006, 09:04 AM)

Green and Tran voiced an issue that caused me some concern and maybe someone can give me some insite. My fiance family name is D- ( double dd ) as opposed to the singe D. All the forms I used a single D - fearing if I wrote Dd it would create more confusion.
You would think the consulate staff , NVC etc will know to deal with this easily. Any ideas ?? Thanks