These days I never recognize a single username on any forum (HN and Reddit, mostly), even tiny sub-reddits. The culture there is created by the masses, so there are plenty of in-jokes only because tens of thousands of people repeat them every week.
Twitter is the closest I have to a site where I recognize a stranger's voice and opinions. But that's typically one-sided -- even in small hobbiest groups, it tends to be the well-known producers talking to everyone else.
It would be 0 for me.
Twitter is better for me in that way, but because is only short interactions, it's not like I'm close to them.
With forums it was way better, for me at least. It felt like family, and in 1 forum I was, we actually had like a 'newbie adoption' thing. With many people there, we actually ended up being internet friends, while on Twitter we might be more like acquaintances.
Look at HN - how many commenters do you personally recognize, except for the ones that are popular because they're part of YC (so for things outside of this discussion forum) or because they also submit articles they're written (so again for things outside of this forum)?
I probably recognize maybe 10 people, and with the way this discussion forum is designed, I recognize them despite the software, not because of it.