There seems to be undocumented requirements for romanizations of city names. Consider a Japanese city like 船橋市。 The official romanization (訓令式 / ISO 3602) would be "funabasi". This is how many people type the name with an IME. However, this is input is rejected, while "funabashi" is accepted.
I'm not sure of a good solution. It may be a good idea to state the requirements somewhere
Hmm, good observation. I guess the site supports Hepburn-romanized names. I believe adding support Kunrei-shiki and maybe Nihon-shiki names too would resolve this issue pretty well.
Given that it's an English site, I'm unsure of the value of supporting the original Japanese names too, but of course it would be neat if it did.
Is kunrei-shiki romanization ("Funabasi") actually considered official? I see Hepburn romanization ("Funabashi") pretty much everywhere (including the official city website [1] in this case). Plus, it's better aligned with how it's actually pronounced.
I'm not sure of a good solution. It may be a good idea to state the requirements somewhere