Editing part of a post for spelling, grammatical or other benign reasons could happen at any time. However, deleting an entire post should only be allowed up until the time of the next post in that particular thread (whether directly related or not to the preceding post). As was suggested by knot4u this can destroy the logical flow of a thread. One could still quote a post in order to make clarifications or to reflect a change of opinion. Also, one could consider with more care what they are about to post before they do so.
