I have since installed another plug-in called Architect by Wapple.
It works for some feature phones, but not all. Here is the response I got from a user who was not able to login:
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the problem seems to depend on the model of the mobile phone. My guess is that either JavaScript or CSS is a root cause..
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specifications of an NTT DoCoMo’s feature phone browser. Other carriers have their own specifications.
http://www.nttdocomo.co.jp/english/service/imode/make/content/browser/index.html
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