I imagine a tiered preferences list would work pretty effectively for this, though it may still run into issues with the same post showing up a few pages later and throwing the preference list off due to different instances having different levels of popularity
Just have a default save to option in settings. Or it could even ask each time.
I imagine a tiered preferences list would work pretty effectively for this, though it may still run into issues with the same post showing up a few pages later and throwing the preference list off due to different instances having different levels of popularity