Comment 36 for bug 66015

FWIW as of the Debian 5.0.1 (Lenny) Live CD, Iceweasel (the rebranded Firefox) in Debian has the same issue. The hyphenated dictionary links are installed by myspell-en-us and you get the underscored "en_US" as well as the hyphenated -> human-readable "English (United States)" in the menu. I could find no bug report for Debian about this, and cursory reading of the Debian Spelling Dictionaries and Tools Policy http://dict-common.alioth.debian.org/dsdt-policy.html also did not reveal anything about the practice of adding both hyphenated and underscored versions of each myspell dictionary.