When trying to bulk add labels, which we frequently do when e.g. tracking feature request / epics, users keep complaining that all previous values are lost. This is because they believe that changing labels is additive, but the way it is implemented, it actually replaces all values with the new single label.
This is counter intuitive and after the bulk operation has been performed, the labels are gone and it is really difficult to manually restore them.
This needs to be fixed / improved since other way less advanced tools offer way better support here (e.g. Mingle).