Before I became a moderator I would flag a single comment as no longer needed and moderators would remove the entire discussion. Flagging more than one comment isn't necessary for users. And as the system supports declining all of the flags by declining one flag, you can more easily have the negative effects of declined flags effectaffect your account.
I personally don't believe the exchange was:
- Obsoleted by age. Where comments on older posts can become outdated. For instance, if technology changes a decade after a comment is posted. Or, 
- Conversational. As one user was telling the answerer that the answer was not an answer and should be a comment. The answerer indicated it was an answer. This was relevant to the post. 
When flagging for a moderator you sometimes are rolling the dice. Different moderators can see different situations in different lights. I do not think the comments should be deleted.
 
                 
                 
                