instiki markdown vs Redcloth

I installed instiki and it works great. The default setting is to use
'textile' markup engine and I love it.

I love that if I just put google.com then it is convereted into a link.

I have another app where I use Redcloth. Here in order to a link I
need to do this.

"Google.com":http://google.com

It's my understanding that instiki is using Redcloth as textile markup
engine. Then why do I see different behaviour in instiki and my app.
In my app typing google.com is rendered as it is without any <a
href=""> etc.

Thanks