We have a couple of requests from users, so we decided to share this workaround with you. If anyone has comments, questions, or better ways - please, feel free to share them here on this topic 
The content about the comment can be retrieved using script using <% %> inside the notification body
Comment is added:
<%
const fibery = context.getService('fibery');
const entity = await fibery.getEntityById(Entity.Type, Entity.Id, ['Comments']);
const documentSecret = entity.Comments[entity.Comments.length - 1]['Document Secret'];
const commentContent = await fibery.getDocumentContent(documentSecret);
%><%= commentContent%>
And this is how the result looks like
