Halliday & Matthiessen (1999: 27-8):
The concept of reactance is particularly significant for our purposes where it involves a relationship between an ideational category and features of other metafunctions, interpersonal or textual. For instance, the interpersonal grammar provides for participants, within the ideational dimension of the clause, to function as Subjects; but this potential is not in general open to circumstances, and this is a principal reason for distinguishing these two classes within the ideational metafunction. Among reactances from the interpersonal and textual components of the grammar, we could mention the following:
interpersonal:can/ cannot serve as Subjectcan/ cannot serve as 'focus' of alternative questioncan/ cannot serve as Wh elementtextual:can/ cannot serve as Themecan/ cannot serve as 'focus' of theme predication (it is... that...)can/ cannot be presumed by substitution/ ellipsis