Comment Function?

[isabel...@gmail.com]

Hello

I would like to implement a comment function where logged-in users can
post comments to something (a post or an image). Should I store a
reference of the comments-object in the something-object or the other
way around.

Replies should inform all commentators by email about the new comment.

Is there a short example on how to best do this?

Thank you,
Isa