I've looked at this a bit more. There are more
Apparently, no-one converted the 5.0 titles in the wiki to 5.1 when
"normalization" was turned on; there are pages that can't be accessed.
(!) for example, try this (Malayalam for "fish"):
that gets normalized to 5.1, which is a redirect to the 5.0 form (in
this case) which is normalized back to 5.1. (there is a variation in
the 5.0 form too that complicates it) The content page exists (I can
see it in the XML dump), but can't be accessed because there is no way
of referring to it.