What is acceptable is correct. The English language is defined by usage. There is no such thing as L'Académie anglais. How a word is pronounced in Latin is not relevant, not least because it's a dead language.
Spoken like someone who has never learned a second language :p
Well, you're lucky that you started your thread during the one hour the match was on :)
In English you can pronounce it in both ways.
If a foreign word has been absorbed in a new language then it doesn't have to follow the rules of the original.
For example, in Italian you use the word "film". But in Italian you don't say "films" when it's plural; in Italian the plural of "film" is still "film".
You see, it doesn't follow the English rules.
Well, you're lucky that you started your thread during the one hour the match was on :)
Okay, mate, I will think of some other controversial topic to post about in a more dangerous timing, then 
I love controversy (of course when it always ends in a smile)
In English you can pronounce it in both ways.
If a foreign word has been absorbed in a new language then it doesn't have to follow the rules of the original.
For example, in Italian you use the word "film". But in Italian you don't say "films" when it's plural; in Italian the plural of "film" is still "film".
You see, it doesn't follow the English rules.
Believe me, there are italians who really say "films" as it shoud be, but I understand your point
Anyway I suffer a wee bit when I hear "fiantchetto" but I suppose this is my problem, not everybody's
I am also trying to cope with the word "panini" (roll or sandwich). In Italian "panini" is plural. So you have "due panini" (two rolls) and so on. If you mean one roll you would say "un paninO". So yes, I suffer a bit when I hear someone saying "I just had a panini", as much as I suffer a bit when I hear someone saying "I will have two paniniS"
@manfredmann: I am not even sure whether the word fianchetto is ever used outside the chess lingo or not. I cannot think of a situation when you can use it if you are not talking about chess. So I think we two agree - at least we two! in this thread - which one is the correct pronunciation: fianketto! 
But fian"CH"etto has NOT been absorbed into the English-speaking chess world! Only a novice says it this way. Once in awhile you hear some little kid or noob say the "CH" and everyone cringes like ... fingernails just scratched a chalkboard.
I guess Yasser Seirawan knows nothing about chess then.
Anyway I suffer a wee bit when I hear "fiantchetto" but I suppose this is my problem, not everybody's
I am also trying to cope with the word "panini" (roll or sandwich). In Italian "panini" is plural. So you have "due panini" (two rolls) and so on. If you mean one roll you would say "un paninO". So yes, I suffer a bit when I hear someone saying "I just had a panini", as much as I suffer a bit when I hear someone saying "I will have two paniniS"
aha yeah that's funny.
But then again, in Italy they say "box" to mean the garage. So you see, nobody is perfect!
In chess my biggest pet peeve is that most people can't spell Giuoco Piano.
In English you can pronounce it in both ways.
If a foreign word has been absorbed in a new language then it doesn't have to follow the rules of the original.
For example, in Italian you use the word "film". But in Italian you don't say "films" when it's plural; in Italian the plural of "film" is still "film".
You see, it doesn't follow the English rules.
But fian"CH"etto has NOT been absorbed into the English-speaking chess world! Only a novice says it this way. Once in awhile you hear some little kid or noob say the "CH" and everyone cringes like ... fingernails just scratched a chalkboard.
It's in all English dictionaries, e.g.
http://www.thefreedictionary.com/fianchetto
So it's been absorbed and it's now an English word, regardless of its origin.
I am also trying to cope with the word "panini" (roll or sandwich). In Italian "panini" is plural. So you have "due panini" (two rolls) and so on. If you mean one roll you would say "un paninO". So yes, I suffer a bit when I hear someone saying "I just had a panini", as much as I suffer a bit when I hear someone saying "I will have two paniniS"
I´m glad you started this thread, maybe you can answer a question which has given me many sleepless nights ... 
What do you call a single strand of spaghetti? Is it a spaghetto?
Greetings from an Englishman living in Berlin who can´t stand the fact that Germans in pubs here play "dart" and not "darts"!
Anyway I suffer a wee bit when I hear "fiantchetto" but I suppose this is my problem, not everybody's
I am also trying to cope with the word "panini" (roll or sandwich). In Italian "panini" is plural. So you have "due panini" (two rolls) and so on. If you mean one roll you would say "un paninO". So yes, I suffer a bit when I hear someone saying "I just had a panini", as much as I suffer a bit when I hear someone saying "I will have two paniniS"
aha yeah that's funny.
But then again, in Italy they say "box" to mean the garage. So you see, nobody is perfect!
In chess my biggest pet peeve is that most people can't spell Giuoco Piano.
I nearly never heard the word 'box' used instead of garage. Sometimes it is used for storage rooms or similar, and very very rarely to mean where you park your car. Garage is garage in Italian (pronounced in the french way, of course! ahahahahahah)
Fianchetto is too fancy a word. I just call it a bishop job.
In English you can pronounce it in both ways.
If a foreign word has been absorbed in a new language then it doesn't have to follow the rules of the original.
For example, in Italian you use the word "film". But in Italian you don't say "films" when it's plural; in Italian the plural of "film" is still "film".
You see, it doesn't follow the English rules.
But fian"CH"etto has NOT been absorbed into the English-speaking chess world! Only a novice says it this way. Once in awhile you hear some little kid or noob say the "CH" and everyone cringes like ... fingernails just scratched a chalkboard.
It's in all English dictionaries, e.g.
http://www.thefreedictionary.com/fianchetto
So it's been absorbed and it's now an English word, regardless of its origin.
Just because it's in the English dictionary doesn't mean that you pronounce it "CH". LOL, i just went to the site you provided and clicked the little speaker goodie next to the word. Try it.
the two in the top left say it with the "CH".
But nevermind the audio, look at the IPA. It's correct both with the "CH" and with the "K". And it's correct because the dictionary says so ;)
I am also trying to cope with the word "panini" (roll or sandwich). In Italian "panini" is plural. So you have "due panini" (two rolls) and so on. If you mean one roll you would say "un paninO". So yes, I suffer a bit when I hear someone saying "I just had a panini", as much as I suffer a bit when I hear someone saying "I will have two paniniS"
I´m glad you started this thread, maybe you can answer a question which has given me many sleepless nights ...
What do you call a single strand of spaghetti? Is it a spaghetto?
Greetings from an Englishman living in Berlin who can´t stand the fact that Germans in pubs here play "dart" and not "darts"!
Yes, one strand is spaghetto (from spago, string. Spaghetto means literally small string). But nobody uses it, unless you are from Rome so you say, in dialect, "famose du' spaghi" (let's have spaghetti: literal translation: "let's have two strings!!!) Now you did not really mean you had sleepless nights about this!
Fianchetto is too fancy a word. I just call it a bishop job.
Fianchetto is not that fancy. Definately "bishop job" sounds totally yankee (and I am saying this with a wink, so no bad reactions )
there is nothing more tedious than chess pedagoguery over pronouncications
language changes over time to meet the needs of a culture
It's not that tedious, I thought that many english speaking people may be interested in knowing the origin of words from other languages and how they are pronounced. Okay, now it sounds tedious, but I did not think it was
Yes, one strand is spaghetto (from spago, string. Spaghetto means literally small string). But nobody uses it, unless you are from Rome so you say, in dialect, "famose du' spaghi" (let's have spaghetti: literal translation: "let's have two strings!!!)
Thanks for clearing this up!
Now you did not really mean you had sleepless nights about this!
Well, not many ...
Yes, one strand is spaghetto (from spago, string. Spaghetto means literally small string). But nobody uses it, unless you are from Rome so you say, in dialect, "famose du' spaghi" (let's have spaghetti: literal translation: "let's have two strings!!!)
Thanks for clearing this up!
Now you did not really mean you had sleepless nights about this!
Well, not many ...
ahahahaha I was sure about that
lol! I didn't think I was starting such a controversial topic!