«إِمَّا أَنْ تَكُونَ بِمُكَفِّرٍ»
Innovation may be of a kind judged to entail unbelief, or of a kind judged to constitute grave religious deviation without reaching that level.
Mukaffirah: a position classified by qualified scholars as entailing unbelief under the relevant criteria.
Mufassiqah: a position deemed sinful or deviant without that classification.
These are technical categories, not permission to issue careless judgments about individuals. Application to a particular narrator requires identifying what the narrator actually held and considering the appropriate conditions and evidence. A sectarian label or an unverified accusation is not, by itself, a complete critical investigation.