Halliday & Matthiessen (2014: 374):
In an incongruent nominal group, the post-Deictic may correspond to an interpersonal Adjunct in the related congruent clause. For example, in
Immediately, the religious groups of the city were embroiled in an angry dispute over the alleged invasion of a man’s right to freedom of religious belief and conscience.
the incongruent nominal group the alleged invasion of a man’s right to freedom of religious belief and conscience corresponds to the more congruent clause allegedly a man’s right ... was invaded, where allegedly serves as a comment Adjunct.