Is the Identity data type supported in versioned SQL Server geodatabases?
No. ArcSDE doesn't support columns when the Identity property is set to True in SQL Server. Tables or feature classes with this property cannot be edited in ArcMap or registered as versioned. The reason the Identity data type is not supported with versioned data in ArcSDE is because there is no way to coordinate an identity field on the business table and the delta tables (adds and deletes).
The following error is received when attempting to register a feature class containing a column with an Identity data type as versioned.
"Failed to register as versioned Invalid column data type [Database.owner.Feature_class]"