Hi Jaceb,
I think it's just a marker, so gecko knows that this node is included in collection business.
Yes, it is a special case, see [1]. It's used to cannonicalize interface pointer so that it may be used as an identifier in cycle collector graph. It's not a real interface and it should not cause reference change.
Alistair, your bug is probably somewhere else. If your patch "fixed" it, it indeed suggests a refcount-related problem somewhere else.
Yes, the patch appeared to "fix" the issue. I'll see if I can track the problem down.
Best Regards Alistair Leslie-Hughes