You go to the file location:

Steam\steamapps\common\Left 4 Dead 2\left4dead2\ems\admin system

Open the "settings" file.

You change where it says "DisplayMsgs = true" from true to false to disable the message in the chatbox.

And you can use the console command "scripted_user_func" to hide the commands instead of the chatbox so that other people don't see them.

For example:

scripted_user_func give,rifle_m60
scripted_user_func god,nick
scripted_user_func z_spawn,tank,5
scripted_user_func cvar,z_tank_health,10000

Note: replace spaces with commas to make it work.

Or you can use the / key instead of ! in the chatbox to hide the commands from view.

For example:

/give rifle_m60
/god nick
/z_spawn tank 5
/cvar z_tank_health 10000

引用自 Maur0：

Or you can use the / key instead of ! in the chatbox to hide the commands from view.

What are the difference between "/" and "!" ? Does using "!" will make it not hide from view?

引用自 Ｊａｋｉｙ：

引用自 Maur0：

Or you can use the / key instead of ! in the chatbox to hide the commands from view.

What are the difference between "/" and "!" ? Does using "!" will make it not hide from view?

/ ---> Hides the command typed in the chatbox.
! ---> Reveals the command typed in the chatbox.

When you put /give nick rifle. Only you see the command, but other people won't. Unless you typed it incorrectly, then they will.