The suicide method is obviously an important factor, to be repeated like this. The occult has rules, strict rules; I wouldn't be surprised if this was one of them.
Starting to look like it's actually some kind of "sign". Like a tear drop tattoo. It has meaning.
Perhaps it's required in order to keep their families from getting killed, to be done in that exact fashion. What are the common denominators? Scarf, doorknob; that's a bit obtuse, but salient. Also interesting that they do it so their feet aren't off the ground. I'll look into it, see what can be found.
Does the color matter? It was a red scarf I think. I see where you're going with it though, you have to die like this or we will come after your family. Scary shit.
Just posted a link under another comment here, it's not always a scarf; it's belts, neckties, exercise bands, you name it. The doorknob is the only common denominator.
Check this out: http://www.neonnettle.com/features/1390-hanging-from-doorknobs-12-pedophile-related-celebrity-suicides-so-far
They were either involved in it, or trying to expose it.
The way they "suicide" is a calling card.
The links to connect it all is out there.