Just a little technical detail:
It looks like when the postings in response to a particular topic exceed 12, the next posting is no longer shown on the current page but is moved to a new page. This is what happened to "On the subject-verb agreement question" in the Use and Misuse section. Note that the subject title is now marked « 1 2 », indicating that you should turn to the next page by clicking the #2 tab on top of the page.
So, to continue to follow the thread of the discussions, just click the #2 tab and you'll be brought to the continuation of the discussions of that particular topic.