Of course spirits can't read or write. Reading, writing, talking (basically anything to do with the 5 senses) are all limited to the physical plane of existence.
However, there have been
reported instances of spirits talking/writing etc. Such things may be up for debate.
Spirits or 'ghosts' are people who are struck in the astral plane, i.e., they haven't crossed over. So they are in limbo- they are neither here on Earth, nor are they in the higher dimensions of the spirit world, which is where those who have crossed over go.
As for spirits leaving behind notes... we can't really adjudge these things unless there is enough scope for research or investigation to determine whether it was indeed a spirit that left behind such an item. However, there are thousands of cases where spirits use mediums or psychics to leave behind messages. The most noteworthy form of communication being automatic writing. Look it up if you can.
Edited by pinkfreud - 14 years ago