If I understand you correctly, your reasoning regarding unpleasant associations with burning already assumes that he did it.
If he didn’t do it (and we don’t know yet wether it was him or, for example, Amelia Bones), he wouldn’t have unpleasant associations with the method of Narcissa’s death, only with the fact that it was ascribed to him. So there is the possibility that he didn’t do it, and doesn’t have negative associations with burning that would be brought up when burning transfigured stones or tablecloth or whatever.
If I understand you correctly, your reasoning regarding unpleasant associations with burning already assumes that he did it.
If he didn’t do it (and we don’t know yet wether it was him or, for example, Amelia Bones), he wouldn’t have unpleasant associations with the method of Narcissa’s death, only with the fact that it was ascribed to him. So there is the possibility that he didn’t do it, and doesn’t have negative associations with burning that would be brought up when burning transfigured stones or tablecloth or whatever.