Question

It looks like when insertBefore() or insertAfter() has the same element as the origin and the destination, the element is deleted. Is my understanding correct?

$('#foo').insertBefore($('#foo'))

Is this a feature? If so, what other gotchas are there with these functions?

Answer 1

It actually seems that it is a known bug (not a feature), although there may be an incoming fix (1.9 release).

From the bug comments:

Since jQuery.domManip passes in a fragment, jQuery.clean moves #x to
the fragment. Later when it gets to the callback in jQuery.after, the
original parentNode is gone.