I'm an idiot. I was feeling mildly insecure about sending a message to someone I might know... which would be weird and awkward. So I didn't want to message him via my gmail account, because my email address is my full name. I used my yahoo account instead.
Except I forgot, because I haven't used this account for anything besides junk mail in more than 10 years, that my yahoo preferences are set to give my full name.
Oh well. It wasn't a security decision, just a saving-face one.