Editing a post change the author and category !

Good call. It is not possible.

The editing option was originally conceived for the posts that were been published with the plugin, so the author and the category were already set inside the txt file you saved in your folder.

For now, you have to set the category using [category] tag. Further, there’s no [author] tag, so the original author will be overridden anyhow. You can’t do much.

However, I’m working on a new release and I will keep in mind this problem.
I hope it will be ready soon.

Thanks for your feedback.