It's almost certainly a sock.
I remember however when Mr Ghostface and Darth Venal were initially speculated to be duplicate accounts Moth3r retracted that proposition even though they had the same IP address and were posting similar 'thoughts' and appeared on the forum on the same day within the same hour.
There are vectors that can produce confusing IP information.
My external IP reads that I'm posting in Glasgow because my provider's server is there and I could share my internal IP address with a lot of different homes and presumably businesses too because of the way the paths are allocated. The IP is also registered in Amsterdam to a Berkshire company.
As I recall Venal and Ghostface were both 'working in the industry' in the same room on the same Harry Potter film.
Venal sadly went more OTT than usual and got himself banned but Mr Ghostface is still around.
I assume that Nebula would have to be in the same part of the world as Angel (he is Greek but may be on holiday).
Nebula could be using a proxy service but the chances of two people on the same forum generating the same IP via a proxy are as far as I know nil.
Strong stuff that Ouzo.