Is there plugin that show ajax comment “form” inline?

Maybe this plugin can help you out: expand-comments

Good luck.

Edit: Wow. I’m a bad reader. I thought you didn’t want to scroll a-way down ON the single page….

Let me add more info specifically relating to what you say, but it’ll make more sense AFTER my intro (sorry)…

Here is somewhat related info, sorry.

That original website is down right now, but what I did on one of my blogs was “float” my comment section so it would appear next to the comment form, and then wrap around below it.

Why float the comments and not the form? (Aside from comments typically coming first in the default template) Because then when there are no comments, it still shows properly (the old way).

This doesn’t help with a long post above, strictly, but it may give you ideas.

You could also try putting the form in the sidebar, but I’m pretty sure it only works to post from the comments template, so it can’t go in sidebar.php, but instead add a sidebar div into the comments.php template for a small comment form. 🙂 (You’d put that at the end of the comments template.)

I’ve even added meta, like categories, to like a sub-sidebar for single pages only. (The same could be done with an extra mini form, although, it would need to be coded after all of the single.php coding, and be in comments.php, so the form would be on the bottom of that aside.)

It’s that same site as the form, here’s a sample post:

http://bagdreamblog.com/obama-bag/

(Sorry if things drastically change there in the future.)

So to show a little comment form on the index, first there is javascript readily available, not even necessarily for WP, that shows/hides with a click.

Then you’d add an if (is_single()) { to your regular code in comments.php, and add if(!is_single()) { (or perhaps some alt) to a small comment form.

I don’t know if that would quite work though. 🙂