After upgraded to 2.1.3 from 1.5x, i notice the preview under the posting area, is sometimes very useful, but somehow, some of us might not have a good internet connection, and will be a bit lag or slow on connection. Even for publisher, it might even drop your CTR(this is what i heard).
So i try check out all the codes, and found out that there is 2 way to disable the preview, without installing any plugin.
Read full tweak on Disable preview in admin post.
You will notice the file that you might be download is the same file which it is resided on your server, few lines added, and it is done. No plugin, and easy.
I am not sure whether i am allow to do this?