It bans some versions of this, but it can't ban all of it. The obvious way is fully banned and hard to get away with: pay someone to delete unflattering things about you on Wikipedia. But, you can do a much more costly, slower, but much more likely to be acceptable version: you can buy a newspaper and arrange for that newspaper to write flattering articles about you. Since those articles qualify as a primary source, you can then have someone update Wikipedia to include things from that article using the article as a primary source. That doesn't delete the unflattering things, but it pushes them down the page and surrounds them by flattering things. If you're a billionaire, you'll find a way to get the articles edited in a way that is permitted by the Wikipedia rules.

I don't know about how they're good at detecting it.

Look up at the story of David Woodward spamming his own bio on all Wikipedia languages.