the scoreboard(objective, key, value) function in scarpet isn't able to reset scoreboard values, which makes it impossible to reset scoreboard values with a key that contains spaces. since the scoreboard() function does accept keys with spaces, but the /scoreboard command doesnt, there is currently no way to reset such keys.
So setting a scoreboard key with a value of null should reset that value like /scoreboard players reset does.

hmph, easier said than done. I can't do it, cos the resetPLayerScore mthod doesn't like being called, and when I copy pasta code, new code won't be called, etc.

you can do it:scoreboard('Score_name',player,null)

ah no wait you can't. I see waht u mean. It 'resets' to 0