Absolutely not. This is a bad ideea.
I even don't like the function where you can edit your own post.
Most of the time all this could be very nice, in the most perfect of worlds this is how things should be.
As not even B1 is perfect...

this doesn't work as exspected. The most inflammated flaming threads here has been closed by mods, but most of the time not until they really believed it was time to close to them. This will for certain be abused - abused though out of somebodies point of view, not from another. You are invovlved in your own thread and then maybe don't see things really clear.
Good customs should be to read your text carefully before adding/submitting. Then face it: you have sent it and now it is there.
I say: Remove ability to edit posts!
Why should discussions get closed when they appear to be outlived? If they really really are outlived, then they are kinda closed as noone will reply to them...