you will effectively make NGUI mark the scene as edited continuously.Checked right now - scene not marked as modified on each call of "mRenderer.sortingLayerName = value;", it means - they compare values internally and mark scene as dirty only on change.
Getter is currently not used by NGUI at all.Why not fixed finally possible GC allocation even on getter? Its public api method and can be used by anyone with GC side effect.