Halliday & Matthiessen (1999: 218):
Finally, some adverbial groups are interpersonal in function — the speaker's comment on the figure, like sensibly in sensibly, they didn't argue 'I consider their behaviour sensible' (contrast they didn't argue sensibly 'in a sensible manner'). These lie outside the ideational structure of the clause: they are not serving as qualities in the figure realised by the clause, but rather derive from features within the interaction base.