you would probably want to have a second table that you use to store these comments.
use a relational column to relate the comments to the user:
commentID - Primary Key
commentUserID - relates to the users.UserID column
then use data assist to create pages to mange the comments. In Data Assist, you can set the commentUserID column to be a Menu, and set it to dynamically use the Users table, use the Username for the label, and the UserID for the value.
this will allow you to select the appropriate user from a select list when adding the comments.
when a user logs in, their iD is stored in a session variable.
on the page where you show the comments, you can use a recordset that filters the commentUserID column on the session created by the login.