The usage string commands.scoreboard.players.list.usage is not defined in lang files. The following command gives the output of "commands.scoreboard.players.list.usage" instead of a usage message:

/scoreboard players list mbaxter likes cats

Normal usage of the command would look like this, and works fine:

/scoreboard players list mbaxter

This command lists objectives registered to the player mbaxter. The usage string appears intended for informing users that the list query only needs 3 parameters ("players", "list", player name), as it is only sent if the command matches /scoreboard players list <player> <more...>.

I believe the text is meant to be:

/scoreboard players list <player>