So a quick disclaimer, I have been at 10k behavior score for a very long time and I am aware that if you stay at 10k it works – you don't get so many toxic players.
Second disclaimer – I'm toxic and don't wanna convince anyone I'm not, but good games have systems that encourage a player like me to NOT be toxic, is the point. Or punish them for being toxic, if that's what you like and I can personally attest I have never been punished for being toxic.
However, a few months back I dropped below 10k to about 8k and I realized how terrible the system is. It's incredibly top heavy, so that any decent human stays at 10k and everything even below is all animals. The problem is, there is no real incentive to behave decently and no real punishment of behaving badly (below 10k) – so animals get worse. I'll explain that part later. But the fact is, as soon as I dropped to about 8k I saw that people do not use the report system as intended. Ever. The player that is reported is 9 times out of 10 someone they did not like or someone who had a bad game – oftentimes the best player of a team, who animals find a random reason to hate. Perhaps its extra bad because I'm in Eastern Europe and I get plenty of arabic, russian, turkish or even iranian players who just don't speak english and whenever they group up will report the outsider (I understand basic russian and turkish from CSGO so I can tell what they're saying). But even when I get western european players, I just never see them reporting toxic players. Ever. Because of this it doesn't actually matter if you're positive, nice or try your best. So you have no incentive at all to be nice – hell, if you think yelling at people makes them perform better (as most instinctively think in multiplayer, in the heat of the moment) you are actually incentivized TO YELL because I've yet to see someone report when they win and all 5 played.
And on the other hand I realized how damn easy it is to become an animal and become even worse. Once you realize you'll get reported totally randomly and you have a decent 10-15 games, mute yourself, only ever communicate for game stuff, whatever, then see the behavior score report and it either didn't change or went down, you start hating all your fellow players who report for 0 reason. And you stop caring. Had a bad day? Probably shouldn't take it out on players in a dota game? Who cares, your behavior score is out of your control anyway, let it rip.
I'll likely get downvoted to hell by everyone who won't read my arguments and will just go "lol just stop being toxic im 10k for a year", but I should specify I don't even care about my own games so much, I play turbo and very rarely unranked for fun (and if I'm totally honest it's a bit of a relief that I'm already down, so playing techies is viable :P), I am just commenting because I'm shocked at the absolute animals you meet below 10k and that these people need help, desperately. Hopefully at least this part people will read.