I had a bunch of thoughts about this then realized I mostly don't care enough to defend any of them. Here's a vastly reduced list of random thoughts:
Current system works alright, any similar system will probably work alright as well as long as the available reactions line up with the kind of trivial responses posts are likely to evoke (agree, disagree, poster is turbo mega gay, informative, etc). The measure of success here is that people don't make those trivial posts and instead react. Too much friction to reactions and it won't meet that need. Everything else seems secondary.
How about a reaction system where the reactions are only visible to the person who made the post and the person who reacted. You could still base the highlighting system off the information and it might reduce the distorted 'points scoring' aspect of the whole thing. But then, will some people feel a private reaction to the poster is insufficient, and would they then revert to making trivial reaction posts in the thread instead of reacting?
You had issues with the forum restore a while back because the way reactions were implemented was like some massive absurd table with a bajillion rows. Since you're re-implementing, consider serializing reactions as a column on the posts table.