Can we get option to give more luck to people, who commented giveaway

No, but (after asking support for permission) you have the option of making private giveaways and stating custom rules such as "entrants need to leave a comment" or something along those lines.

people would just make 420 fake accounts and give themself +420 luck on their mainaccount and it becomes a masterrace.

This would encourage bots to augment in numbers rendering the human population at Steamgifts to a lifeless pulp, then proceeding to conquer the world and using our liquified form to feed human clones that will be used to produce bio-electricity.

And how would we sort out generic comments left by autojoiner bots, that, I'm sure, are still very much here?