The point that has been missed in the great knaidel (knaydel? kneidel? kneydl?) controversy is that the real problem isn’t the spelling of Yiddish words in Latin characters. It’s the spelling of English words in Latin characters.
In the Hebrew characters that are native to it, Yiddish has been, for the most part, ever since undergoing a series of modern spelling reforms, a consistently spelled language. (The one exception to this is its large number of Hebrew-derived words, which have retained their distinct Hebrew orthography despite 20th-century campaigns, particularly in the Soviet Union, to spell them like other Yiddish words.)
This means that when educated Yiddish speakers read a Yiddish word on a page, they know how to pronounce it even if it is unfamiliar to them, and that when they hear one spoken, they know how it should be written. Although their way of pronouncing what they read may vary according to the regional variety of Yiddish that they speak, it will remain invariable for any given speaker.
This is true, in one degree or another, of most European languages, which have had spelling irregularities caused by hundreds of years of speech developments ironed out in modern times. It is not true of English, in which no significant revision of spelling has taken place since the 18th century. The result has been that modern English spelling is wildly inconsistent.
A native English speaker encountering a new word in print may have no idea how to say that word aloud. (If, for instance, the word — I have just opened my dictionary at random — happens to be “susurrant,” do I say “SOO-seh-rint,” “SUH-seh-rint”or “suh-SUH-rint”?) If an English speaker hears something that sounds like “sick-a-tricks,” how does he write it? (The answer is “cicatrix.”) The same small sound can be spelled in English as “you,” “yew,” “hue,” “u” (as in “usurer”), “yoo” (as in “yoo-hoo”), “eu” (as in “euphemism”), “hu” (as in “humor”), “yu” (as in “Yukon”), and “Hugh.”
Written English has letters representing consonants that are pronounced differently without rhyme or reason (why do we say “get” with a hard “g” but “gem” with a soft one?); letters for vowels that can be pronounced in six different ways (think of the “a” in “father,” “fat,” “many,” “another,” “ball” and “gate”), and letters that aren’t pronounced at all (“h” in “hour,” “p” in psychology, “gh” in high, “t” in “whistle,” “n” in “damn,” “b” in “lamb,” to name a few). It’s a nightmare for spellers, whether they’re in night school in China or first grade in Kentucky. It’s no wonder that you can win $30,000 for spelling “knaidel.” You might also have spelled it, apart from the more common alternatives, “knadle,” “kneighdel” or “cunadile.”
It’s thus pointless to argue about the word’s correct English spelling. Sticklers for protocol, and serious Yiddishists, may prefer “kneydl,” which follows the transliteration rules of YIVO, New York’s Institute for Jewish Research, the closest thing there is to a Yiddish academy of language.