Last modified: 2013-02-25 11:14:04 UTC
It is possible to add the same item as value to a property twice. There's no reason for this.
There are very few constraints in the system now, and I think it would be necessary to add some reasoning to why specific constraints should be added. Especially there should be some clear arguments as to why a specific constraint should never be violated.
*** Bug 44882 has been marked as a duplicate of this bug. ***
Closing as wontfix, this is the expected behavior.