resetting and adding scores can only be done to specific players. the @a and the @p don't work with resetting the scoreboard and the @a doesn't work with seting/adding score
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I'd like to mention that the @p still does not work with "/scoreboard players reset @p" in 13w05a. As this bug is also reported here and report is marked as Fixed, could this be looked into again.
To be added on the not working list: /scoreboard team join TeamNameHere @p
This is not fixed, and while your at it make it to where you can use a player var in a /say or /tell command
You need to use Join not add for the command
/scoreboard teams join TeamName @p
and you can use the @a, @p and @r in say and tell commands.
It still does not work, also that was a typo and thank you for finding that... also did you know when you type in the command in chat it will add the player @p to the team! (also editing post to fix typo)