How to read a tx's comment? How can I retrieve the comment field from a payment transaction that I made from my QT wallet?

I can see the comment when I click "Show transaction details" in my QT but I cannot find a way to do this from the RPC console.

Any ideas?
Use the listtransactions RPC call, and look for a field named comment:

$ bitcoin-cli listtransactions
[
...
    {
        "account" : "",
        "address" : "msj42CCGruhRsFrGATiUuh25dtxYtnpbTx",
        "category" : "send",
        "amount" : -0.00001000,
        "vout" : 0,
        "fee" : -0.00000225,
        "confirmations" : 0,
        "txid" : "0ecdc2da9266635349ad04b7374eb1032919c34e7949e60cec198b47e31d2f26",
        "walletconflicts" : [
        ],
        "time" : 1427561024,
        "timereceived" : 1427561024,
        "comment" : "COMMENT" &lt;--- Here
    },
...
]


Note that this comment only exists in your wallet, and is not sent across the network. The other party to the transaction will not see it.