The problem is that right now I save another copy of the entire post every time something changes, even if it's a single letter. If I allow multiple unlimited rescrapes, storage usage can go quickly very fast...
Is this really going to be a storage problem? I can imagine only a fraction of the posts gets edited many times.
I'm more interested what happens when a post is rescraped, and didn't change: do you keep track of the fact that it wasn't changed on a certain date? I think that could be valuable information later on, to estimate when a post was edited.