Disliking posts was a crucial part of the old forums. Some players have some pretty crazy/unimformed ideas, and I feel like marking these with dislikes helps readers know that the OW community doesn’t agree with what was posted.
Edit: Somebody in the comments had their comment hidden because it was flagged. I guess this is the new way to deal with troll posts, although this can definitely be abused, like it was in this thread.