Using SQL Compare version 11 for Microsoft SQL Server, I can exclude a user from the schema comparison:

<exclude>Role:MyCustomUser</exclude>

This works fine for excluding the user.

However, the comparison engine does not exclude the user's mapping to roles. The script includes sp_addrolemember commands for the excluded user.

When excluding a user, I expect their role assignments to also be excluded.

I suspect this behavior may exist with object exclusions for other object dependencies. Have not tested other scenarios.