Recently, There seems to be so many multiple accounts among various rating ranges.
In top 10, there is kiwikiwi, who became Legendary Grandmaster in 2 months. He should be a great genius, right? There is better hypothesis: He is someone's smurfing account.
In Div2 contests, many black-colored people are at top of the scoreboards. Why there are always a lot of talented newcomers? You will know the reason.
Why don't Codeforces ban those multiple accounts? They ruins contest scoreboard and rating system. For example, kiwikiwi "absorbed" other participants rating for about 5-6 contests to be Legendary Grandmaster. On those contest's scoreboard, there were always him on top pages.
One account for one person. That was the rule. Smurfing accounts should be banned.