More on topic I have used the arrows mostly as a sign of agreement or respect.
Or as for me ,If anybody adressed allready what I was going to say anyway or even better I just give him a plus 1 for that. But I do give a minus for bad language or an insult.
If you have a diffrent opinion? it’s ok. We agree to disagree, but if you start to insult somebody as a protest I do minus that.