I would like to get comments on the following Idea and my response to it. I believe that one could make a case that this is a bug.

IDEA: Reporting on Full Comments in Lightning vs. Classic (Sean Davis 1 year ago)

When running a report on full comments within the Task Object in Lightning we are unable to see full comments unless we export. When we run the same report in Classic we are able to see full comments when we run results. Is there a reason why full comments are limited in the Lightning view when we run results?

My response to the idea:

We have a button on our account page which filters a general activity report to only show results for this account.  This is a CRITICAL feature for our social workers who view this report whenever talking to clients.

Full Comments is not actually a field in the Activity object.  It is specifically available for reporting only.  Therefore I would say that if the user explicitly calls out that field, he/she should be able to get it in full. 

I just want to emphasize that my user's will not be willing to transition to Lightning without this feature.