Of course you can be harassed on Blind; I've seen it happen plenty of times. It's no different than the kind of pervasive harassment that caused the death of Yik Yak.
Is it harassment to know that other people don't like you? I've seen (and held) opinions on both sides: middle-school me would've said yes, adult me says no.
There's a large difference between not liking someone, saying how much you don't like someone in a public space and actively spreading rumors or saying how much you'd like someone fired.
In that sense, the middle school analogy is apt considering how people can behave.