AD: The prefix is my initials :) - my only HN account is a shared one with a co-op organisation I work through. I use AD to distinguish who's commenting... however my co-workers have yet to use this account ha!
Your initials form a word used as a disclaimer often. And shared HN accounts are not common.
If you replace "AD:" by "Adrian from Endian writing:", people won't have to wonder what "AD" means, and waste their and your time on asking (you will probably get this question a lot otherwise).