It takes a lot of trust for him to let someone close, period. She's gotten glimpses of the real him, some that he intentionally shown to her. Others he hadn't intended at all...

Even if she can't understand his words, the tone is encouraging and praising. At least one of the phrases he's said to her before, though she didn't understand then and won't now. Silken and warm murmurs only for her. Loki wouldn't deny he had talked with and to his lovers before, but for her--they were accompanied by soft brushes of his mind against hers. Little wisps of thought and touch that praised her, welcomed her, appreciated and wanted her more.