I'm not sure why you would want to do this. While it may make some sense to top-post replies in emails, exchanged between individuals, but a forum is designed for multiple users, not individuals, many of whom will join the topic long after it was started and need to catch up before contributing, Trying to read a sequence of posts while repeatedly scrolling up and down makes this a pain of the highest order for the newcomer.
That's why forum's traditionally show posts within a topic in date order. This allows newcomers to read through any topic from the earliest post, or any point in the middle, to the latest and so easily put the most recent post in context. You need to consider other users when interesting in a forum.
If you are a regular participant in a forum there are a number of ways to jump to the latest post without needing to upset things for new users:
1. Keep a browser tab showing the forum open and simply refresh the page when returning to see the additional posts since you last viewing of the page.
2. From the forum Home page select "Topics View". This produces a list of posts in date order, most recent first, rather than by folder. It also tells you in which folder/sub-forum the post was made.
3. On the page listing the topics in any forum/sub-forum, click the date link in the "Last Post" column. This takes you directly to the most recent post regardless of how many post or pages of posts are involved. (A long topic becomes paginated.)
4. When viewing a topic, consider switching from "Classic" to "List" or "Threaded" view. These other two views initially hide the bodies of the posts, and show only the date, author, and first line of the post. Click on post concerned and it opens to reveal the full body. "List" shows posts in date order. "Threaded" shows an indented list so you can see who has replied to what within the topic. This is extremely useful in a complex topic as someone coming late to it will often want to respond to something posted early on.
In addition, if you subscribe to a daily digest, you may click the link at the top of the post snippet within the digest. That will take you to your browser, open the correct forum page and scroll directly to that post.
Also be aware that under the "More" option against any post there is a "Permalink" option. Use this to copy the URL of the individual post within the forum, when directing others to a point of interest on the forum.
Just a Volunteer Nabble Helper - because the nice folk at Nabble have helped me!