Filipino spelling variations account for the many discrepancies found in translated texts. A translator will use a spelling that is correct, then the reviewer or back translator will "correct" the spelling, without underscoring that the "correction" is a spelling variation. This puts the forward translator in bad light, since the source will think that spelling was taken for granted.
Among the variations, the choice of vowels - the use of "o" or "u" (kompanya vs. kumpanya), "e" or "i" (eksamin vs. iksamin) has always been an issue. In the old days, there were only three vowels in the language. The vowels (o and u as well as i and e were interchangeable as far as pronunciation was concerned).
In other variations, the presence or absence of "y" in spelling Tagalog/Filipino words is also an issue (Diyos vs. Dios; Iglesya vs. Iglesia etc). Also problematic is the deletion or insertion of the vowel "i" in words preceded by the consonant "s" (pasya vs pasiya; konsensya vs konsiyensiya etc.). Again, apply the rule of consistency in this case.
Habit or a regional way of speaking (dialects) have long dictated the spelling that rules in a locality (that is, spelling as spoken). In the case of "o" and "u" and "e" and "i" vowels, it is not fair to strike out a spelling as wrong just because one's ear dictates that it should be one and not the other.
Here consistency must rule, that is, spelling a word in one same way all throughout the document. As long as the spelling is correct and consistent (the dictionary helps but most English to Filipino dictionary do not contain all the variations), there should always be a note on why a Filipino variation spelling is preferred.
One more serious concern is the spelling of words when transliterated, that is, when the sound of the source word is transferred using the Filipino "syllabic" way of spelling (collaboration into kolaborasyon; specific into ispesipik or ispesipiko). Unlike Spanish, Filipino words are not inherently "feminine" or "masculine". However, maybe, because the Philippines was under Spain for three hundred years, some transliterations of borrowed words either end up with an "o" (masculine) or with an "a" (feminine). This gender-izing is not always necessary - that is, "ispesipik" is acceptable.
In all technical, medical, and legal translations, this issue demands a closer attention from the proofreader. Translators and proofreaders may consult the Spelling Guide (Gabay sa Ispeling, (c) 2008 by Galileo S. Zafra et. al. published by the Sanggunian ng Wikang Filipino - UP Diliman). This Guide is a product of long, ardent discussions among people from the academe, linguists, publishers, editors, and writers.
When to Retain the Source Word
Sometimes, transliterations are found in the most current English to Filipino dictionary, but if the target user is familiar with the source word or if the source is used in ordinary conversation, it is better to retain the source (if English, retain the English spelling). One example in medical translation is the word "side effects". This can be translated into "mga masasamang epekto ng gamot" (BT: bad effects of drug), but at the risk of rendering it more vague for the end user who may not easily recognize this translation to mean "side effects." Transliterating this word into "sayd epek" may be an option.
Another concern with transliteration is when Filipino or Tagalog will use "p" for "f". Since "f" is already a part of the Filipino alphabet, it is okay to use it in the spelling of a borrowed word with that letter.
Then, there's the issue of transliterating "ph". Since Tagalog doesn't really have many words with the "f" sound, Filipinos don't hear it, and therefore don't pronounce it. Words with the "f" sound may always end up sounding with a "p". Although written Filipino may use F, editors and proofreaders must not be subjective and change or "correct" the first spelling choice involving p, f, or ph. (Note: although "Philippines" is spelled with a Ph and the first two letters must be pronounced like an F, most people will say they come from the Pilipins - P sound.)
Other "adopted" consonants try to outsmart the Tagalog spelling and depending on which university is promoting what, the indecisiveness goes on: (x and not ks, thus sex instead of seks; chance not tsans, research not riserts, etc.).
All practical linguists must be informed even about the debate that goes on, especially reviewers, linguistic validators, and back translators. "Correcting" a spelling subjectively will affect the quality of the work of the translator. As long as the first choices are correct and consistent, any subjective change should be avoided.