As has been pointed out, some songs have 'accent' built right in and, frankly, singing songs like The Dowie Dens O' Yarrow in a straight english accent would sound rediculous. But at this point we're really looking at a language difference, rather than just an accent.

However, I don't find it at all surprising that people pick up accents/quirks/habits in songs from other singers. We pick up our own accents from how the people we grew up talked, it's no different learning the same from the singers we grow up with. In fact it can be quite hard to differentiate the melody from the arrangement until - as Trevek says, we get to know the song better.

As Terry McDonald has pointed out, sometimes we don't know that a song can be sung a different way. If I can, I like to find more than one recording of a song I like, just to hear what the differences are. But often this isn't possible, or practacle - it can get real expensive real quick having to buy albums for just one track...

But then there's also the point that the accent/quirk is the thing about the song that you like, that makes the song in your ears. At this point we're down to simple preferences. And what's meat to one is another's poison. Captain Birdseye critisised Jim Carroll for not liking a certain singer, but that's the point isn't it? It's all subjective. If you find a particular habit or accent or 'quirk' in someones singing annoys you, that's your point of view. Others may have a different point of view which is equally valid.

People that deliberately go out of their way to adopt quirks etc? I tend to find that as they continue singing a song, they'll lose the 'adoptive' bits, whether they mean to or not, unless those quirks really sit well with their voices.

Most of us, I would say, sing in a style that has evolved with us as we've learned songs and techniques. A hotch-potch of quirks and habits but eventually all of a piece and our own.