Talk:Ai wa Itsumo Kimi no Naka ni / Futsuu, Idol 10nen Yatterannai Desho!?/@comment-46.5.61.44-20140610093335/@comment-131168-20140610120437

As long as something written in katakana is clearly meant to represent an English word we'll tend to represent it with the proper English word, even if it doesn't quite sound like that.

Your note about how イドル would be pronounced differently is correct--and when it comes to foreign words being represented in katakana, it's the norm to go with what would be the closer to the correct pronunciation rather than spelling. To back this up, here's J Wikipedia's article about idols, under the title アイドル.