I can't attest to how it used to be, but now at least they are in a section labeled "User Contributed Notes". The notes can be voted up or down, so hopefully the dross sinks to the bottom.

I do agree with the sentiment though that these unofficial notes should be taken with a grain of salt. In my experience, they have been more help than hindrance.

Maybe that's how it was, but it has a clearly defined header that says "User Contributed Notes" now, with up/down vote counts on each comment.