list archive URLs changing

Some time in early May, a commit was made, and the author wrote me a message
reminding me to revisit it when the first-class aggregate feature was
complete. The message had this link:

Clicking on it today, I find a commit that has nothing to do with
the feature. Hunting around, I believe I found the intended commit, which is
a few messages later in the archive:

Similarly, what was recorded as
seems to have moved to

seems to have moved to

I don't have specifics, but I believe I've seen other archive links
change like this. Did the archive get re-indexed, or have there been
any other changes?