I have started using Evernote a week ago and this is already bothering me a lot. Yesterday, I accidentally tried out simplify/remove formatting, all my tables were gone and couldn't get them back with undo nor ctrl+z, so I had to start all over. Today, I accidentally clicked remove row in stead of column, same story.
I have googled the undo problem, and it appears to exists for several years already. I find this very worrying to read that people lost part of their notes because of malfunctioning of the software. Because of this I am looking into other note taking software products!