I decided to keep an eye on a player one of my friends played with. This person was either completely new at the game, or trolling.
OP.GG said he was likely to be placed in bronze 2 after the match I first noticed him.
After 10 losses that were blatantly his fault, he got placed in bronze 4.
If you're on a fresh account that has never participated in ranked, shouldn't you end up bronze 5 after 10 losses?
Maximum Morde1 votesNo. Bronze 5 is reserved for people literally worse than intentional feeders. AKA, the people who actually lose to intentional feeders.
WoonStruck2 votesExcept people in Bronze 4 and higher get placed in Bronze 5 all the time, even with relatively successful placement matches.
Maximum Morde1 votesBecause placements aren't going to put you higher than the year before.
WoonStruck1 votesNobody expects them to. You have to win at least 7/10 in order to get placed where your MMR currently stands.
Dabrick011 votesIt depends on how he played. If he fed all game for most of the games, then he would be placed bronze 5.
However if his team was too heavy to carry and he still did OK, but then lost, then he could be placed higher.
Looking at the page you linked, i have no idea how the fuck he got any higher than bronze 5. Some of his builds are atrocious (Graves with 
is my favorite.)
If you want some advice, get him to pick a main champ and mode and play that shit over and over again in Norms.
venomous frost3 votesin-game performance is in no way related to MMR gains/losses
Mysticman894 votesIn-game performance has no impact on your MMR, only whether you win/lose, and it's your final MMR that determines where you place.
The amount your MMR changes when you win/lose depends on the average MMR's of the people on either team, so premades and longer than average queue times can sometimes produce games that more significantly impact your mmr than others.
So for example, an new unranked player who duo'd with a high gold would be in games with a higher average MMR than his own, and so the system would expect him to lose, and have less harsh MMR penaltys. As such, if he went 0-10, he might still place high bronze. If he went 10-0, he'd have increased mmr gains from every match compared to if he was solo, and so could place mid-high gold (I've even heard of fresh accounts getting placed plat 5 after going 10-0 while duoing with a high mmr friend).
By contrast, if someone duo'd with a bronze 5, their individual mmr would be higher than the teams average mmr, so their mmr gains would be minimal, and their losses much bigger. Going 0-10 would almost certainly place them bronze 5 (and heck, even going 5-5 might still leave them low bronze, since their mmr losses would outweigh their mmr gains), while going 10-0 would probably still be low-mid silver.
Even someone going purely solo can still have some variance in their placement due to MMR as a side effect of long queue times or by random chance getting placed in a match with other premades, so it's hard to ever say for sure where someone will end up based solely on their W/L ratio.
EndlessSorcerer1 votesYou have to be really, really bad at the game to drop into Bronze 5.
It takes far more than 10 lost games you prove yourself worthy of it.
WoonStruck1 votesI just find it odd because people all between Bronze 4 and Gold have been placed in Bronze 5 after relatively successful placement matches.
I know its based on your previous MMR, and I've never had an issue being placed in Gold personally, but it seems odd that if you aren't gold+ MMR by the time the previous season ends you're almost better off with a fresh account.
KłedGod1 votesI got bronze 4 and I won 7/10 games in placements this year was hoping form bronze 2 but it doesn't matter much because I made it to bronze 2 some what quicker then expected. If I recall right I only won about half my games the first time I did placements and got silver 5. The game basically will always place you at a reasonable rank your first time to see if you can really hang or not and if you can't you just drop in rank.
IcyPepper1 votesIs the difference between Bronze 4 and Bronze 5 worth getting up in arms about?
Placements aren't about deciding where you go, it's about your mmr. If you're really concerned about how he placed, check how much LP he gains and loses on wins/losses. If he's gaining lots and losing little, your concerns are not misplaced. Otherwise, eh, he's going to drop fast.
Commander Javik1 votesI should feel lucky then . OP.GG was saying that i will be in b5 after finishing my placements . When I finished them , i had 4W/6L and got placed in B3 . Last season i did something like 2/8 and got placed in b4 , where my friend did 10/0 and got placed B5 .
Spice POWAH1 votesseriously? well then i'm lucky I got in silver 5 for going 9/1 in placements