It's a bit off-topic but still related to default settings for external links. I haven't tested the acp of 0.7.0 yet and I was wondering if there was something like a whitelist for external links? Then if someone click on an external link we can activate the warning page "you are leaving the forum", but if it's a sub domain, a root domain or a trusted url (youtube) for example we don't show this page.

@julian said:

I imagine if href is missing, this.href would be undefined, no? smile

No. 😛

I was surprised that it's been an empty string that got checked instead of undefined too, but it seems I'm to adapted to jQuery ^^

This is because you use the DOM-element rather than jQuery to get the href:
document.createElement('a').href === ''
$('<a></a>').attr('href') === undefined