How to make an address as on picture?

Look at this forum screenshot and tell me is it possible? I can't find how.

It can be very useful if you want to separarte answers for several people.

Error has gone. And now I need to up this topic, because pictire is uploaded. Please, answer the question if you can.

NickRimer while you can just note the followed by the name of the account (which will notify it that someone tagged him on the topic), I do not think you can simply click somewhere to have the tag pop up in the reply.

although this link is for usernames tag only, on the forum.

Aphrodite

Hmmm.. well.. simple way..

Thank you a lot!