It is possible to delete a signal only by being its creator. The delete option is available in the edit screen. Before confirm, a window with any element involved by the operation is shown.
It is possible to delete more signals at once. Clicking the "Edit signals" button in the signals list, the checkboxes will be shown next to every signal created by the user. Selecting the checkboxes and then on the "Apply changes" button, the actual deletion is done.