The FAQ addresses some of these points. If you keep your username sufficiently unique and secret then no-one can edit your list. I wanted a really low barrier to entry for trying out the site i.e. no email addresses or login via a social media service.

The service shows you albums from the last 5 years but that could also include re-releases (which might explain the Slayer weirdness).

Thanks for trying it out and the compliments.