In ArcGIS for Desktop (10.2.2) using the Maplex labelling engine, layers can be configured to NOT flip automatically. This option appears in the Label Rotation Dialog. I have been unsuccessful finding the value for a given layer from within ArcObjects. I have searched for the property on MaplexLabelEngineLayerProperties and on its OverposterLayerProperties. I've successfully located all of the other label position/rotation properties available on the Label Rotation dialog, except for the setting to Keep Label Upright. Any assistance directing me to where this property is exposed is greatly appreciated.
This property is IMaplexRotationProperties::AlignLabelToAngle which is on the MaplexRotationProperties object accessible via IMaplexOverposterLayerProperties::RotationProperties.