The title ought, at the very least, to mention "Haskell", don't you think? Why? Why should it mention Haskell? Should it also mention Extended markup language in the title? Or should it mention Haskell because of all the people on perlmonks searching for nodes discussing Haskell? But the node doesn't discuss Haskell. In fact, it's parent node has more Haskell related content than the HaXml node. But the parent node is title "Re^10: Better mousetrap (getting top N values from list X)", although it doesn't discuss mousetraps at all (but was the title of this node, or any of its ancestors considered? Bet not). It doesn't even discuss lists, or getting the top N values. But that's fine. But a reply that mentions HaXml gets all the flak - flak it wouldn't have had if it used a title mentioning mousetraps and lists, while not discussing any of them. Come on, give me any good reason why we're discussing whether or not "HaXml" covers the content of the article, and why we are not discussing the mousetrap title of its parent.
In addition, I believe that, as a general rule, node titles which look like root node titles (i.e. there's no "Re:" in front) should only be used on nodes that look like root nodes. I think, in general, that data shouldn't be duplicated. Whether or not a node is a root node or not is already known to the system because of its lack of ancestors. The newest node page doesn't have a problem with it - it's not using the existence of a leading 'Re:' to determine where on the page to list new nodes.
In fact, one must resort not only to ancestor nodes in that thread to discover the context, but to other non-ancestor nodes in the thread. Oh, right. It's common that a node that's referring to more than one node in the thread reflects that in the title. Like say, all the nodes benchmarking the proposed solutions to a problem. I think not.
"HaXml" is that much worse, because it does. Agreed. "Re^11: Better mousetrap (getting top N values from list X)" would have told me instantly what the node was about. Just like its parent.