Instead of reloading with the refresh button, reload by clicking on the reply number and that reply will be at the top of the reloaded page. But, you can only do this once and after that, clicking on the reply number will not reload the page. If a thread is moving at a fast enough pace, this isn't a problem and if is moving slow, refreshing with the refresh button isn't nearly as big of a problem. Also, in this case, you can reload by clicking the previous reply number, which puts you almost at the top. Slow loading graphics will throw this technique out of kilter, depending on how many slow loading graphics there are on the thread.
The other problem with FF is the page returns to the top of the thread after posting a reply. The obvious solution is reply in a new window.