Something annealing and other local maxima algorithms do is always inject some noise. Annealing calls this the temperature. So Facebook could ensure that 5-10% of your feed comes from a "region" around where it thinks you stand, then see what you click on.

If you only Like Left, then you keep drifting. But (I assume) they will always include some stuff to the Right of where they think you are as an option. It won't be Far Right, but it will be in that direction.

Obviously, this is a lot of speculation of how Facebook is doing it's feed optimizations, but I expect they provide opportunities to get out of your localized maxima.