quoting Nessari:

Following on from IRC:
This probably supports it being something with unicode; I just tried to make a test entry for < -ō >, and it redirected me to the preexisting entry for < -o >.
I also tested by resubmitting alǰin via the single-entry addition form, and it showed up perfectly as it should.

...yeaaaaaahhhhhhhh...

The name collision thing is a MySQLism that I haven't figured out how to shut off yet. It wants to pretend that diacritics aren't real, based on its misguided faith in the orthographies of certain European languages. In theory it's a matter of setting the right country for the collation order, but I haven't figured out what it is yet or how to make it actually obey.