TextMate not saving files in UTF-8
I'm not an expert in the field, but I believe the reason for this is you probably saved your test file only with ASCII characters. When using only ASCII characters UTF-8 is simply indistinguishable from it. It's when you start using characters that are outside ASCII scope (e.g. accents in other languages, like ąśćż in polish) the difference is noticable.

Try copy&amp;paste the characters I used as an example, save your file again and test it.