The same happens to me...but I think there is a workaround. There are three ways to access the "reply" page/window.
The first is to click on the "Post Reply" button at the top of the thread. I tried that and got the "message is too short" error when I tried to preview my post.
I next tried clicking the "quick reply" icon at the bottom of an individual message and did not check the "Quote message" option box. Lo and behold, that worked!
So then I tried Advanced editing of my posted reply and that worked too.
Using the Quote icon at the bottom of an individual message doesn't give you the error message but whatever you typed in your reply disappears when you Preview it so it still doesn't work
In conclusion, those of us who have this problem need to use the Quick Reply icon at the bottom of an individual message if we want the rest of the world to read our thoughts
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