A thumbs up wont cause too much negativity if any but if it includes a thumbs down then this can cause issues at some stage, i am on the DJI forum (drones) and theres someone thats habitually down voting a few of the longstanding members just because something didnt go his way, but as its a Chinese run forum, little will be done.
I vote a thumbs up or a like button that just shows that the post/reply has been likes by X amount but NOT a dislike button....
PS, i too have asked for this in the past, the problem is, we get so used to Facebook and the ease of the Like button that everywhere else that does not have one just feels odd, for folks that do not use FB or if they do, they dont use it that much then they will not feel the need for the button. Theres many times where i have wanted to just Like a post/reply but felt it didnt warrant any further input.