In my view ideally upvotes and downvotes federate both ways, but I can also see why some admins might choose not to federate in downvotes.
I guess the real question comes down to what you do with the information.
I think currently the sort order is very heavily skewed towards boosts (which I actually quite like), but I do also sometimes wonder how it would look if the sort order was aligned with the reputation system (i.e. boost= two upvotes).
Having both sort options available might be nice, (noting that we'll not federate in any boosts from Lemmy).
If we did federate in downvotes the current sort order (which seems based on boosts less downvotes?) probably wouldn't make sense?
...I'm also be keen to see others thoughts on this!