The mentioning is done by typing @ username , but without the space after @
Often the username is the one between brackets, so: in your case, that would be @ Infoxicao , without the space.
Hovering over someones name might also display the @ name.
To make it more confusing; sometimes the username is not displayed and sometimes only the username is displayed.
In my case, you could use @spikeyxxx . But I read everything anyways, so it is not necessary to @ mention me.
