# Tagging more than one person in a comment

I have noticed then when I first wish to tag someone in a comment with "@" upon typing say "g" choices come up like "gauss" or "galois" depending on which user is mentioned in the thread. However when I want to do a second tag not only do such choices not show up but a yellow box shows up saying

"Only one additional @user can be notified; the post owner will always be notified."

What is the reason for this? Thanks.