website design - Should you place the "add a comment" form above or below the list of comments?

There seems to be very little consistency across most sites when it comes to placing the comment form.

Which do you think is the most usable, above the comments list or below?

Above the list:

• Disqus


• YouTube

Below the list:

• Digg v4


• Wordpress default template


• StackOverflow

Answer

I always prefer to think about the use-case I want to encourage, or that is forced by the nature of the site/audience.

If most of your audience will read the content and immediately want to comment, put it on top. If on the other hand you want to encourage people to actually read what others have commented before them and only the respond, it makes more sense to put it on the bottom.