“Browsing through the archive, I found a few puzzles with answers labeled. What does that mean?”
Sometimes the editors of Spelling Bee will decide that a word which was accepted in earlier puzzles will no longer be allowed in future puzzles. That could be because the word has been deemed too obscure or offensive to continue using, or there might be some more arcane explanation.
Whatever the reason, we do take notice when previously accepted words are not accepted in later puzzles. Since we continue to display complete solution sets for earlier puzzles, we wanted to be sure to mark those problematic words, by way of explaining why you may not see them accepted in the future.
You can see an example of a puzzle with words of this sort here.