ModxTalks: notify of new replies and extra input field possible?

Hi, I'm trying out ModxTalks. So far it looks good, but I was wondering the following: I would like two extra form fields in the comment form:

1) checkbox 'notify me of new replies'
2) input field 'your website'.

Is there maybe already a notify-of-replies function included in ModxTalks that I'm not aware of?
And what files should I edit to add an extra input field?
Thank you!