Just as a heads up - naming and shaming is against boards policy. Make sure you censor out any names (outside of your own) before posting things like this. Thanks!
the reason he's doing that is probably cause his main got banned, lmao.
Based on that chat, it looks like a situation where someone is boosting another account or is taking an alt account into ranked.
You shouldn't post usernames on the boards, because that can lead to witch hunts...
But I'd recommend submitting this screenshot to Riot games in a support ticket. Riot will investigate and if it's appropriate to do so they will ban the player. They can't tell you if they punish the player due to privacy reasons, but you can have confidence that they will investigate them.
You can submit a ticket here: http://support.riotgames.com/
Naming and shaming is against board rules. what you can do is leave a detailed report of what it is he did and why you think he should be banned after the match. hes much more likely to receive a punishment that way.
En: I'm sorry for your friend(s) who had to go through this. The Lux is obviously going mid, not jungle, forcing mid to go jg instead. You're in the NA forum btw, not EU. Role hijacking is a known issue, at least they could've asked for a swap first, before locking in. Atm not much can be done but either dodge or play out and report said player in the post game screen lobby. GL!
Ro: Imi pare rau pentru prietenul/ii tai care-au trebuit sa treaca prin asta. E clar ca Lux a ales mijloc, si nu jungla, fortand persoana designata mijloc sa joace jungla in schimb, lua-l-ar naiba. Esti pe forumul american apropo, nu european. Furtul rolului este o problema cunoscuta, puteau macar sa ceara un schimb inainte sa fi blocat rolul, dar nah. Momentan nu prea avem ce face decat sa parasim jocul curent, sau sa jucam pana la capat, raportand rahatul de jucator in ecranul de la sfarsit. Bafta!