I've noticed few plugins changing the structure of the existing WP tables by adding new columns.
e.g. The Admin Management Xtended plugin adds "menu_order" column to wp_posts table so you can order posts manually.
Is that wise?
Isn't it better to create a separate table for your plugins and then link the data with WP tables data?
Does WP overwrite its tables structure to default when updating to a newer version?
Thanks in advance!