Tried searching but couldn’t find anything. Can the order be changed to newest first within a topic?
Some forums have huge topics with hundreds of pages of answers and are IMO better read with newest-first order, where you don’t really care about the old ones.
If a topic has hundreds of pages of answers and it does not matter to the reader what was said in the beginning, it does not represent quality content. In quality discussions every contribution counts.
Discourse already provides the function of beginning the reading experience where you ended it.
Why would it not be necessary to read all these posts in-between? What makes latest posts more valuable?
Edit: If you don’t care about the old posts, you would not keep scrolling to read them. Do you only want to see the latest updates like, for example, I would want to read in a “news” feed aimed at entertaining me?
AFAIK this would require a plug-in or modification to the core codebase to implement. As a work-around, each topic has the green “progress bar” in the lower-right. You can always click the down arrow to be taken to the last post in the topic.
Also, in case you didn’t catch it from @pyro240’s response:
In other words, Discourse keeps track of your reading position. For example, if a topic has 40 posts and you read 30 of them, it remembers that. If the topic gets 40 more posts while you’re away, it will start you at #30 so you can pick up where you left off. I know that’s not a direct response to your query, but it’s useful and cool. 
You can also enter a topic at the first post or last post by clicking the appropriate date in the Activity column on the far right.
@codinghorror That’s actually really cool. It loads last x posts and then I can scroll back up. Never seen this before. I think that fits my use case pretty well.
Still, it would be awesome if I could tick a checkbox in the topic settings menu and allow it to show entries in reverse order. It would be awesome for twitter-like topics where there is no logic flow between posts and it is preferred to show newest entries first.
Reverse order option would be nice – I was hoping to use it for a changelog.
Its a very complicated change, probably a week of work to wire it up properly without having stuff like collapsed streams, deferred loading and so on working.
That can be useful for embedding a live discussion, for events like a webinar. In those cases you would want the last comments on the top, or the autoscroll of some kind.
Still no updates on this one 6 years later? I miss it badly! 
There are still no plans to add alternative orderings in to topics (order by likes, order by date desc and so on).
This request very infrequently comes up and it is exceedingly complicated to design.
You can experiment with this plugin but the maintainer hasn’t got much time to provide support.
萨姆，您好：
Discourse 现在可以按相反的顺序显示了吗？
谢谢
我们有两个用例可以从中受益：
我们有作为公告频道的主题。例如，“Gitlab 中的新功能”是一个主题，每当有相关的更新时，都会有人回复该特定主题。目前，最旧的公告是新读者看到的第一条内容。用户实际想要的是最新的公告。允许版主/管理员为特定主题反转顺序的设置可以将较新的公告排在前面。
据我所知，Discourse 日历通过添加带有日期的回复来将新条目添加到日历中。
这导致最新的日历条目是距离最远的回复。在我的个人日历中，最新的条目大约在回复的第 200 条。我可以使用时间线，但最好是将最新的条目放在顶部，而不是一直向下。
既然滚动到底部是一个可用的功能，为什么不提供一个可以立即调用它的设置，而不是作为用户操作？或者也许可以自动化？
这将实现让每个读者都滚动到最底部和最新回复的期望结果，而无需实际更改回复的顺序。
我可以看到这是一种不错的替代方案，但对于日历来说，我认为反向排序仍然是有利的。它允许用户查看日历，然后向下滚动一两个项目即可看到最近的事件条目。目前，我需要跳过 200 个条目才能看到最近的事件。