I think you refer to a system as
Reddit voting system.
Many people have armies of accounts that can be used to influence the system and make certain signatures appear first.
merit points still means a kind of excellence for the post/topic.
Personally, when viewing a lot of replies, I give merited posts a higher value.
Ahh!! I don't use reddit, but I understand now how it is about. Certainly, that's a great idea. It can save a lot of time, but, on the other hand, this can discouraged lazy people of reading the answers below.
What happends if the 35th answer is better and nobody reachs it because they think the first is the best? And... What if the merited one is far to be a good answer?
In the other hand, remember that many topics are receiving tons of merits due to the farming instead of quality, so it can be useful for detecting farming or merit abuse, though.