The previous owner coated the gable wall with a black substance, perhaps something like bitumen or tar, no doubt as weatherproofing.

Since old buildings are meant to ‘breathe’, this ought to be removed.

This will require scaffolding: if the pointing is indeed to be raked out and redone, then clearly it would make sense to do both jobs together, along with any other work that requires scaffolding. …Such as removing those unsightly modern PVC barge-boards.