read and write comments in shared reports

Hello family

The need is for :
- enter a comment
- keep the date and user of last entry

I ask for your help on the accesses, the idea is to manage the profiles of users who can read or write the comments in the reports:

we have 3 groups A and B and C : 

- All groups have the possibility to read the comments sent by all the groups.

- Each group has the possibility to write comments on its strict perimeter (A or B or C)

- the group ( C ) has the possibility to read and write the comments sent by the group ( A ) and the group (B)

Thank you for all proposals