I like using votes to determine whether or not it's worth devling into a deep thread. If there's a conversation that goes 5 levels deep, you can just scan the bottom layers - if they're getting votes, then it's likely to be a worthwhile conversation.
Similarly, if there's a bunch of responses with a score of 1 with replies forking off all over the place, having a visible score lets you catch that at-a-glance and avoid bothering with a conversation that is clearly digressing.
Similarly, if there's a bunch of responses with a score of 1 with replies forking off all over the place, having a visible score lets you catch that at-a-glance and avoid bothering with a conversation that is clearly digressing.