Yeah, I love that thing, too. I remember using it a lot back in the day xD.
It's a simple orange line with a red outer glow. Then in the background I added some black strokes for contrast. Usually if you pick colors close in the palette, you can find a contrast that will really make it neon-like. My favourites are shades of red.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory