If the servers you're using are using ULX, it's a log configuration item.
I don't know exactly where in XGUI, but in gmodserverpath/data/ulx/configs.txt
ulx logEcho 1 ; Echo mode
; Echo modes:
; 0 - OFF No output to any players when an admin command is used
; 1 - ANONYMOUS Output to players without access to see who used the command (admins by default) similar to "(Someone) slapped Bob with 0 damage"
; 2 - FULL Output to players similar to "Foo slapped Bob with 0 damage"