have you selected a different layout in Display Settings?

No, I'm using standard Anonymous Monk layout (logged out)

What do you mean? I used the animate function for the scrolling. If I understand you correctly, that's how it should be?

I mean it should be fixed on screen, so if I scroll the content, it remains on the screen where it was left, it floats, like a floating toolbar, it doesn't change its position on screen ; like browser navigation buttons, window contents scroll, the buttons stay on top of window

Right now its added after all the replies -- at the end -- I kinda tend to read from top to bottom, so navigation aids tend to be most useful when they poke me in the eye, like first page somewhere on top :)

See perlre for an example, I believe the magic it uses is  style="position: fixed;"

About draggable, I mean re-positionable -- floating is great, collapsability is great, draggability is the ultimate in control -- it might not matter if this navigation-aid is positioned well by default, but draggability is a great way to see if there is a better position -- jquery.ui.draggable.js