Is Boosting allowed?

So another game passed in silver 2, where I met a midlaner who was boosting a friends account to Gold V. The guy playing being obviously alot better than the rest of the team, maining Diamond 5. This guy has been playing around 20 games for his friend, going 20-1 or something similar every single game. This makes the game alot less enjoyable as in ranked im used to playing people with and against similar skill as me. Now I had a discussion with this player and he said Riot is okay with people boosting their friends accounts to rank up higher. I was wondering if anyone could confirm this for me, as it will affect how I will be playing ranked from now on. Besides that (although I might not be very skillfull), I might consider ranking up for others if they so please aswell in the future.

Please share your thoughts