It looks like this was a larger decision from the lemmy development community in an attempt to eliminate karma farming. They say it’s psychologically damaging, and as someone who looks at them a lot, they may be right.
Here’s a GitHub thread discussing it where our Voyager dev weighs in:
https://github.com/LemmyNet/lemmy/issues/3393#issuecomment-1779400639
You’re making this more complicated than it needs to be.
The simple naive approach would be every time the app sees a post, it can memorize the current score for that post locally. For the user of the app, that should be all their posts right? This doesn’t need to be accurate broad strokes are fine we don’t have to catch votes that happen after we’ve last seen the post
For other users we look at, we could just tally the posts we see when we open the user profile which would be a few that get dynamically loaded I think five or six. That should give us trend data.
We don’t have to engineer anything more complex.
I really think you are grossly oversimplifying the problem.
When I click on any user’s profile, I’m seeing content from a lot of posts that my app instance hasn’t seen before. Each user follows different communities and accesses the app at different times, so each user’s instance will only have data on the posts that they have clicked through when they are browsing. The score calculation that you are suggesting would vary wildly depending on how much overlap you’ve had with that user previously. 5 or 6 posts out of hundreds or thousands would not be enough to consistently see a valid trend.