Threaded discussion UI for my app

In the system I am developing, I need to create a UI for managing customer notes. A customer note is a textual note related to a customer that a customer service representative writes. For example, a note might look like:

Please note that this customer does not like to be called early in the morning. If callback is required, do it in the afternoon.

Also, a note can be "replied to", for example:

Note 1 (written by customer service rep a):

The customer didn't receive her order, what happened?

Note 2 (written by customer service rep b):

It turns out that the customer entered the wrong address

Note 3 (written by customer service rep a):

I have called the customer and asked her for her address. It should be all good now.

A response can only be one level deep, as in the example above.

My idea to present this is as follows:

Have one big grid that displays all the notes (including metadata about each note). Notes that are part of the same reply chain, as in the above example, will appear next to each other in the grid, with the most recent note in the reply chain appearing at the top. To convey that each note in a reply chain is"connected", I want each note in the reply chain to have the same colour in its leftmost column, as in the image below. Is this a good idea? So as you scroll through the grid, you will quickly get a sense of which notes are related, and which are not.

By the way, this is a desktop application written in a legacy framework that can't do very much. So please don't suggest anything too fancy.