Another way it can be implemented is by pinning the very first comment to the top if it was submitted by the same user. That way you keep the form simple with two text fields only.
Whereas all I'm doing here is exposing the text field that was in submissions already, since underneath they're the same kind of obj as comments.
But I think this whole 'bubble popular stuff up' is a tad off. Its too binary, IMO humans aren't all that binary - not all of us anyway. How about you use sliders so people can rate stuff more subjectively and you can also use relative font sizes to size up stuff which is more popular and reduce the font size on stuff that isn't. This does not mean that the text becomes too big or too small - its just a subtle change.
This will allow you to disable this whole bubbling scheme and keep things in a natural chronological order while making it easy to spot popular stuff without adding any cognitive load.
Finally, a discussion board must really have a feature that shows all 'unread' or 'updates since your last post' threads in bold or some sort of highlighting. While news.ycombinator implements the unread piece it would be helpful if it highlighted updated threads also.
How can I be sure you read this comment?
1.My own perspective is that it does not matter whether it is a 6 or a 7 and who interprets it how. That is the whole point of a subjective system it is not objective.
2. I believe subjective systems should not use numbers or other notations and therefore I suggest a slider not 10 radio buttons or a rating system.
3. I do not imply that the binary/objective system is no good. It is good for some applications, I would just prefer a more subjective measure around things which incorporate human opinion.
:)
You know the saying an image is worth a thousand words. ,-)