I think Eve, that you are afraid of the forum becoming full of holes and lose coherency. I suggest that this will happen, but it would be rare and has other benefits.
On other forums I attend, an author of a post is free to edit or remove forever, and it works well in those forums. If I make a mistake, could be I spelt a member's name wrong, and a following post points out my mistake. I go back and correct my mistake. Now the following post complains about my error which is no longer there, but everyone reading it realizes what happened, and the mistake I made does not get propagated as much. If it is a more serious statement I am corrected on, I will often leave the original statement there but strike-through and add an explanation that I was wrong. This prevents giving bad advice or presenting something as fact that was only a rumor.
On other forums I attend, an author of a post is free to edit or remove forever, and it works well in those forums. If I make a mistake, could be I spelt a member's name wrong, and a following post points out my mistake. I go back and correct my mistake. Now the following post complains about my error which is no longer there, but everyone reading it realizes what happened, and the mistake I made does not get propagated as much. If it is a more serious statement I am corrected on, I will often leave the original statement there but strike-through and add an explanation that I was wrong. This prevents giving bad advice or presenting something as fact that was only a rumor.