Places that use systems like this often turn out to be popularity contest cesspools. Oft times, meaningful discussions get dismissed by the system because other posts with far more "likes" are given preferential treatment.
On the face of it, one may look at something with more "likes" than another, and believe that it's clearly more popular, therefore that's the route that Jagex should go down. However, as Kopaka said, a "like" adds nothing meaningful whatsoever. This means there are many risks with adding such a feature to these forums.
Take the Suggestions forums as an example.
Thread A is suggesting that everyone should get 200m for free every week for logging in.
Thread B is suggesting some much needed updates to a particular minigame.
Thread A may be very popular amongst players who don't like working for their money, or don't understand how the economy would react to such an update. This could receive a very high number of upvotes, even though it would be a terrible update for all concerned in reality.
Thread B would probably not see many votes because the subject is rather niche and not frequented by many players, i.e the interest in it will be low. This does not mean the contents are bad though, as the content may be what that minigame needs to increase its popularity.
And now we come to the problem: If Jagex releases Thread B's suggestion, people will complain that something far more popular hasn't been released. If Jagex decide to go with the popular vote, they risk damaging the game. Just because it's popular, doesn't mean it's good.
So for this reason alone, I don't see any need for like/dislike buttons.
There are other disadvantages too. Dislike buttons can lead to mental negativity which should be avoided in my opinion. This is why you don't see such buttons on the likes of FB.
Another is that it's very easy to create accounts en masse to sway votes.
I don't see how a vote system can have a positive outcome.
~A~
18-Jul-2021 00:17:14