Deleting a file did nothing on the live 0.15.5 server, with no error: the menu
items are gated on myRights.mayDelete and myRights.mayRename, and 0.16 was the
release that split rights up. Before it a node carried mayRead, mayWrite and
mayShare, with the one mayWrite covering everything the newer release names
separately — so both items sat permanently disabled.
Widen mayWrite into the four rights the newer shape names, alongside the
nodeType normalisation, and the UI can keep reading the 0.16 vocabulary.