problem solved.
But, seriously, people create new accounts in order to play vs DDK - because DDK are afraid to accept challenges of too high ranked players. Sometimes they accidentally play ranked game and create new account to have [?] after name again.
There should be option to create unranked challenge where others see your rank as [?] , so new account not needed
then more DDK will accept your game and less people will decide to become evil sandbagger.
not everyone have [?] account to play weaker opponents, they just use it for full “no rank” settings collection
there are also just new users, if there will be more [?] challenges, then new users will not look so alien