Just wonder about user data meaning. If I have user defined table it means that it keeps user defined data.

Here the very simple example of filtered index on computed column

CREATE TABLE [dbo].[t2](

[c2] [int] NULL,

[comp_col] AS ([c2]*(2)) PERSISTED

) ON [PRIMARY]

GO

create index ix_comp_col on t2 ( comp_col )

where c2 > 4

GO

So?