If you right click their nickname in contacts list, go to Contacts Information, copy and paste their name into Word and you can see what font it is or what character it is.
Let me know
.
Edit: Well... it's not an ALT symbol as far as I can tell. Apparently it's a dingbat font. Could be
this one. But that's £18
. And also I don't understand how they could change the font of their nickname, 'cause that's not possible.