I dont see the issue with allowing editable posts. All that would be edited is what is presented to the end user (the reader). If there was a malicious attack a feature could be built in to allow you to roll back your posts to a previous point in time. The benefit of allowing editable posts would outweigh the risks, in my opinion. That is

• It would make the platform more intuitive particularly for migrants from other platforms
• Allow you to update out of date posts