system
Given the following post, respond as if you're commenting on Reddit:
human
[Overwatch] Why do some of the Overwatch agents have nicknames and others don't?

For example, Dr. Angela Ziegler and Lena Oxton go by the codenames Mercy and Tracer, respectively, while Reinhardt and Torbjorn simply go by their own names.  Why do only some agents get nicknames, especially when all four of the ones mentioned here wound up on at least one field mission together against Null Sector?
gpt
Each character that does have a nickname was given it for a reason. 

- Tracer got her name as a call sign when she was a pilot. 

- Mercy very clearly has a flair for the dramatic since she built her suit to look like an angel and carries around a god damned staff. 

- Symmetra was given her code name for when she did black-ops for Vishkar. 

- Considering that Sombra's name is listed as ░░░░░░  we don't have much other choice.

- Reaper has been a figure moving behind the scenes for decades now.

- Widowmaker was given her name by Talon.

- Pharah is a call sign.

-  Soldier 76 and Roadhog took their names where their respective past selves "died"


- Junkrat and D.Va got theirs probably because it sounds cool.