This isn't a major problem, but in American English, the usage of "Whilst" and "While" are not the same.
As a grammar search reveals, "Whilst" is generally not used in American English
That's not to say it's completely absent. "Whilst" does find its way peppered into American English, but in general....it is only used as basically a more "emphatic" form of "while", used when you're contrasting a marked difference between two things, often ironically. For example, "Nero played a fiddle whilst Rome burned", would be one of the times where using "whilst" sounds appropriate.
This isn't just me, I'm saying that this sounds really weird to American readership of the wiki.
Well for example..."Bran talks with Osha whilst Hodor leaves to fetch the horses"....sounds very odd in American English. Why is it ironic that Hodor is fetching the horses, compared to Bran talking with Osha? In this circumstance "while" would usually be used.
"Whilst" would still be used for things such as..."Joffrey has Sansa beaten in front of the entire court, whilst outside the Red Keep the peasants are starving." or "Whilst Margaery is aware that Renly is a homosexual, she actually doesn't care, because she thinks the marriage alliance with Renly is very important for House Tyrell."