Let's just make sure we're on the same page... to be clear, you're talking about the Latest Discussions page found here:
https://www.democraticunderground.com/?com=latest_threads
(Or by clicking Navigate > Latest Discussions)
On this page, like most pages on DU4, you should see six "context buttons" near the top. One of these is blue and says "Start discussion" -- another one should be yellow and look like this:
If that button is yellow, it means the threads on the Latest Discussions page are being sorted in chronological order, with the most recent at the top. That should be the default view when you arrive at the page.
Below that, there is what we call the "filter bar" which looks like this:
The image above shows what the default settings look like.
Category allows you to filter the page so it only shows threads from certain categories
Relevance allows you to filter the page so it only shows political threads, or non-political threads
Started within allows you to filter the page so it only shows threads from a particular time frame
Milestones allows you to show or remove posting milestones on the page
The default settings are "All," "All," "24 hours," and "Milestones" -- if you change any of these settings and hit "Go", you'll get a notification in the filter bar which reminds you you're not in default view and allows you to change it back. The notification looks like this:
So to address your issue -- does the above make sense, and is that what you are seeing when you visit the Latest Discussions page? If that is not what you are seeing, or if you don't think it's behaving the way it should, please let me know. The more information you can give me about what you're seeing, the better.