Mentioning a personal tragedy in an academic style paper. Is it allowed?
Since you are the editor of the volume, it is you who decides whether it is allowed. There isn’t any codified set of rules specifying whether any given content is allowed or not. That’s exactly one of the things editors are supposed to do - to edit.
Consider whether it makes sense to have such a paragraph in the volume given its topic and purpose. If you think it is appropriate, allow it. If not, don’t. If it is a borderline case, you can raise your concerns with the author and suggest that they change or remove the problematic paragraph, without requiring it outright.