I think "consistency" depends on your point of view.
I'm guessing the current function names are based off the W3C DOM Spec:
insertBefore:
http://www.w3.org/TR/2002/WD-DOM-Level-3-Core-20020114/core.html#ID-952280727
appendChild:
http://www.w3.org/TR/2002/WD-DOM-Level-3-Core-20020114/core.html#
I propose the following function name changes for clarity and consistency:
Rename:
domxml_node_insert_before -> domxml_node_insert_node
domxml_node_append_child -> domxml_node_append_node
Remove:
alias to unlink (in favor of the more consistent unlink_node)
domxml_node_new_child() (in favor of