what the OP is wondering about is certainly something that happens , by looking at the reputation section or the known-alts topic, you can see that many people get accused for using alt account with some poor evidence.
Mikewith's first contribution in the known alts thread was some
five hours ago so it's interesting he's speaking with such an air of authority.
As OP of the thread he's so graciously referenced, I can't recall reading that happening often - rarely would be a better description. You'll find abuse in forms you won't even know has happened to you such as person's who have given you trust are peer pressured into removing their trust. Might sound like Butt Hurt, it's not, it's just answering your question with facts.
Good luck.