Valve gifts smurfing players a lump of coal for christmas that immediately bans them upon opening it

Using an alternate accounts so you can play with lower ranks and easily win them. It's a form of griefing in video games and against the rules.

Experienced player creating a new account to stomp on low rank players.

It would probably just autoban a few days later.

The players who lost their accounts aren't hanging around on unranked matches to stomp newbies. They'll want to go into ranked matches to get their level back up. Also, activity on both the new account and the old one would sus out deliberate smurfers

Im not sure there is a way to stop it from going into your inventory

an unavoidable dialog pops up to open your gift

It is!