There are pronominal person prefixes which indicate person of subject and object.
Derbyshire assumes, that the pronominal marker indicates first or second person Object, if the subject is third person or includes third person (first person exclusive), in all other cases the person of the subject would be indicated. This would mean, there is no Portmanteau.
I first person
II second person
III third person
I+II first person inclusive
I+III first person exclusive
Number of subject and/or object is indicated by suffixes which mark tense, aspect, mood and in some cases subject person as well. Transitive and intransitive verbs use the same markers. There are four sets of such suffixes:
The nonmotion imperative paradigm distinguishes between four persons of the subject.
The motion imperative paradigm distinguishes between two persons of the subject.
Nonimperative mood paradigm.