yes, anyone with an account can edit.  It's a strange and extraordinary experiment in public knowledge.  One of the most interesting things around, in my view.

I was at a lecture once where the lecturer criticized the information on WP.  I was at the back of the room with my laptop.  Before the lecture was finished, WP was correct.

Everything on WP is traceable.  There a great deal of very carefully thought out information about how WP works, in WP itself.  One starting point is here.

There's a very good book about it by Jimmy Wales, who founded WP.  Silly title, but excellent book.

Best,

Dominik