depends, what exactly you need to achieve and where ...
may be you might first explain how did you make that an approver see other comments...
- by default task comments are store with task in task list (so not visible on item). so if do not give approvers direct access to task list they shouldn't see them
- you could copy approver comments to an item and store each approver's comment in a separate list column and show to each approver just 'his' column
- you might store comments to a separate list
and several other possibilities, hard to say from your description what might fit you.
Could you rephrase the question to make it more clear?
Are you able to explain exactly what each user can and can't see please?
Retrieving data ...