I've seen that the first merchant found in Undead Burg is selling the Orange Guidance Soapstone item. The in-game description of the item is:
Online play item. Write/view/rate message.
Messages transmit to other worlds, where they are rated. Also, rate messages of others.
In Lordran, the flow of time is distorted, and messages allow Undead to assist (or deceive) one another.
So, it appear that in contrast to Demon's Souls, I need this item to leave message to other players. What I'm wondering is whether or not this is a consumable item? Will I need to buy a new one each time I want to leave or rate a message?
And isn't the description misleading? Because, I've not yet bought it, but I'm already able to see some message on the ground.