When ticket form is loaded (editing an existing ticket) and search automation is enabled for Comment, a list containing search result from Forum is displayed below the search box as soon as you type in the Comment field (press Space to execute the search).
Function for this control is same as described in Description section except Add as link and Add content functions also works when you have entered the keyword in the search box directly. Based on action respective link or content is added to the Comment box of the ticket.