this depends on how your data is set up but generally this woulod be steps to take
group by case (likley a PK field liek caseid or caseno)
place comments fieeld on the group footer.
suppress the detail section
this will show you the last comment per group.
if you have a datetime field trhat you can use to make sure the details are in order you can sort on that field.
you could also conditinally suppress using that field
NOT(maximum(table.datetime,table.caseno)=table.datetime)