Pragmatism and Inerrancy
I'm wary of stories like this contributing to what I'll call "progressive fundamentalism" -- the insistence, or at least hope, that the original meanings of scriptures and other things are supportive of progressivism, and the ostensibly anti-progressive versions are later corruptions. While there may be a certain schadenfreude about hoisting the conservative fundamentalists by their own petard, I think we should be careful of attributing too much significance to the original version of a thing -- particularly an "art" or ceremonial text like a poem or hymn. The author's intent is not sacred.
As a counter-example, consider the UU hymnal. The UUs took some hymns whose original version was indisputably sexist -- clearly calling God male -- and made them gender-neutral. The type of progressive fundamentalism that would get excited to learn from Sam's post that "Yedid Nefesh" is "really" non-sexist would have to accept that these ostensibly non-sexist UU hymns are "really" sexist, and therefore we must either accept their sexist portrayal of God or reject them altogether as fundamentally tainted by their sexist original conception.
My answer to Sam's question is based on the philosophy of pragmatism: it depends on what your goal in singing it is. If your goal is to express your conception of God, and your conception of God is a non-sexist one, then you should sing the original "Yedid Nefesh" and the revised UU hymns. If your goal is to have that kind of comfortable coming-together that is achieved through reciting familiar words, then you should sing the revised sexist "Yedid Nefesh" and the original sexist versions of the UU hymns. There's nothing inherently wrong with an (honest) revision of a text, if it makes it more suitable for a legitimate purpose.
Things get a bit trickier when the text in question is a scripture. "Scripture," as I'm using the term, is a text whose value comes from it being evidence of what God thinks. Faithfulness to the original -- however sexist or not it may be -- is worthwhile in the case of scripture because we can make the original hypothesis that it was in the original version that God most clearly expressed him/herself (though that's not always true -- e.g. some Christians believe the King James Bible was as, if not more, divinely inspired than the original texts that King James's translators were translating). But even this issue can be subsumed under the pragmatist rule -- if your goal in using a text is to figure out what God thinks, then the correct version is the one closest to God's inspiration.