I'll be honest - I was thinking authorization (a11n?) - so I didn't read it closely enough. But despite that, and being on HN from almost the beginning (with a different account I lost the password to), I still didn't know what a16z was, though I do recognize Andreessen-Horowitz.

Opposite for me, I've seen a16z tons of time on HN, and also the domain where sometimes, but the full name would have meant nothing to me.

I didn't either. This is an ancient debate that can never be resolved completely, though — because the articles that HN submissions point to don't follow a style guide and there are always assumptions about audience priors. Best to just resolve it and move on.