Recently I learned about the deletion of my posts that I submitted about an year ago. To me it meant loss of knowledge that the answers and comments provided. What are the reasons for deletion of posts from the Stack Exchange Site without intimation?
Question threads which are closed and not edited and reopened within a certain amount of time are considered abandoned and eventually get deleted by the system automatically.
Generally, if the post gets closed and not reopened, the default would be that they in fact contain no content worth preserving.
That being said, false positives (closed although they maybe should not have been closed) are not out of question. But to be fair, they regularly are identified by votes and/or flags and corrected.