Jagex has stated that obtaining the IP through RS is impossible.
Because as seen through the corporeal beast glitch they are always aware of what is happening with their game and we all know that if they were aware of such an issue they would immediately want to alert people?
I'm not saying it's absolutely a client leak but I think the options are getting pretty slim since most things have been eliminated at this point:
Discord leak
Skype leaks
Teamspeak leaks
IRC leaks (nobody uses this anymore anyways)
3rd Party Clients (OSBuddy, Runeloader, etc.)
Looking at all the different victims there is little to nothing in common other than the Jagex client.
People who don't / have never installed 3rd party clients, on a fresh IP, without entering discord etc. and only going in their own teamspeak have been DDoSed by the individual mentioned in the original post. Additionally another content maker (Wiggled) was DDoSed by this individual and he swapped accounts with a friend who hadn't been on his account before, logging into his and expecting to be DDoSed when his friend was attacked by YE IM BALLIN, however it was in fact his own account, with his friend on it, that ended up being DDoSed with there being literally no way of the DDoSer knowing who was on the account? These were both covered on the videos I posted on the first page of this thread I believe.
Here is another video:
Cba watching all 20 minutes of that honestly but it keeps getting passed around so i'm fairly sure it's relevant.