No, it would be a moderating nightmare. I also think it's a good mindset for the site. Just like how you can't take your words back in real life you can't take them back on GaG. Be mindful of what you say.
i think it's b good, but if i were an admin, id say you're only allowed to edit it once, so you need to be careful with your editing. that way, the feature isn't abused and people actually take the time to think about what they're writing.
The thought of it sounds like a good idea, but implementing it and really seeing it in action can cause problems. Pelple will take advantage of it. Maybe proof reading it once, twice, three times lucky will help. They can always go with that idea. But give you a restriction on how many times you can edit a post. Like once only.
There are both benefits and disadvantages to this idea. On one hand, it greatly helps with any typos or misconceptions the OP can clear after making the post. On the flip side, however, it essentially gives 5x more power to the trolls over any given user.