How are the reports created by default and how did you solve the problem of comments?

Hi

I would suggest that you open a ticket with support so that someone can look into your requirements with you and offer advice specific to these requirements. They can also look at the excel file together with the cubeviews you have created and discuss your design approach of using a currently unused UD for your commentary. 

I think you would benefit from being openly able to discuss the specifics of your requirements, details of which wouldn't be appropriate to post on a public forum. 

Thanks