Mack.

Deleting a post could change the meaning of a thread. Editing a post after a certain amount of time can do the same. Therefore, no deleting, and only a limited edit time. :)

scinario. user "A" posts a question, user "B" wants to help and starts typing out a very long detailed answer.

Shortly after posting user A finds the answer on his own and removes the post and subsequently the thread. At the same time user B is sweating blood and tears writting the defnative meaning of life. Finaly he/she clicks post and gets a 404 page not found. Not much fun.

Mack.