Allow sorting if not logged on or default to newest to oldest
Default non-logged on people to see posts within groups sorted newest to oldest.
Allow sorting for people who are not logged on.
Sorting is a lot harder on the new forum, and impossible if you're not logged on... I like to pickup the iPads and check the forums. You can't see what's going on unless you logon. Otherwise I get years old post at the top mixed with post from days or months on the same page. The old post may have 10-12 months of comments but yet still shows at the top. I liked being able to see what the latest issues and posts in a group without having to logon each time.
The default for everyone, logged in or not, is to put topics in order newest to oldest. I opened up a different browser and hit the forum and I spot checked a few categories but did not see any that were sorted oldest to newest.
If you are seeing "old" topics they are likely stickies and not recent posts. Look for the pushpin icon next to the topic title. If you can link to a specific example of a category showing old non-sticky posts first when logged out, I can look into seeing what is different about that one.