There seems to be a missing URL in your email here.
As a user, I find the navigation particularly frustrating. The headings “by subject,” “by author,” and “by date” are displayed as if they were actual data entries, which creates the misleading impression that every author is named “by author” and every subject
is “by subject.” This significantly affects the readability and accessibility of the content.
I don't understand the suggestion either ... in fact, is there even a suggestion? You've said there's a problem (but I don't understand exactly what you mean) but not how to solve it.
As Oliver said, those links are for the index of all mails for that month sorted **by author** or sorted **by date**.
Also, I don't think we control the precise format of those archives, it might just be what mailman generates.