[Kaderin Triste]

Originally Posted by Coda

That's just a regional accent. There are a lot of cases of vowels that are pronounced like a short i in some accents and like a long e in other accents. It's not an error, not any more than underemphasizing R-sounds in New England or British accents.

This word is actually one of the few examples where my wife's accent slips out. She usually speaks with a generic American accent (technically, "neutral midwestern") but she grew up in Mississippi and every once in a while the way she'll say a word reveals that fact.

One of the ways you can tell that it's an accent feature is that it's systematic -- when fully realized, people who speak in this accent also say "pill" as if it were "peel", "bill" as "beal", "till" as "teal", et cetera. (The pattern suggests that "will" would be pronounced like "wheel". I've heard that a few times, but it's context sensitive -- in phrases like "will go" the heavy de-emphasis of the helping verb can make it come out almost like a shortened form of "wool" instead.)

Does your friend by any chance replace some long E sounds with long A sounds? e.g. saying "tea" a little more like "tay"

Well....unless Montana is divided into vastly different linguistic regions, it's not a regional thing. Same as me he was born in MT and has lived here all his life. And does not replace any other long E sounds with long A.
It's literally just windowseal/windowsill.

Update: he has informed me that it's actually a medical thing where his frenulum I think it's called, is farther forward than most people, so it's easier to do vowel sounds where the tongue doesn't have so much vertical movement. Apparently he also says "pellow" instead of "pillow".