Comment Field provides a field that can hold simple comments.
It holds the uid of the author, timestamp, and body (comment text).
The display is configurable, making it possible not to display the author
(for example, in cases where the author is always the same) or timestamp.
This allows administrators to leave simple comments on entities such as
orders, and possibly for users to comment back (if they have the permission to edit the field).
Note that all editing is done on the edit form, new comments can't be added from the view page.
The module doesn't aim to be a full comments solution, which would require
comments as entities, threaded views, anonymous commenting, etc.
Important: I don't have time to develop this module further. Either ask for commit access, or investigate alternatives such as Reply (full entity-based comments replacement) or Message (perfect for the activity stream use case, order comments posted by admins and customers, which is the usecase this module was used for).