If you’re looking for something that can vote a post up and down with thumbs up and thumbs down types of tags, my personal opinion is that the dislike or thumbdown button is not needed. You can already filter topics by number of likes and number of posts.
In the main screen, you can select view by Posts, Likes, Views, and Activity date. This would basically give the same functionality seeing which topic is the most interesting, I do see that it won’t flag the most controversial topics. Though, I imagine that the controversial topics would have a lot of posts in them.
If you just want to express your opinion in a post. There is great support for emojis.
There are a ton more here.
If you’re looking for a thumbdown button, I’m curious to hear what type of behavior you think it will foster.