[bug][ui] Dark mode reaction button styling

I think there might be an issue with the reaction button styling on dark mode. I found it confusing trying to understand if I've already reacted to a post or not

Here's what it looks like when I haven't reacted:

And here's what it looks like when I have reacted:

Compare that to Github, again first when I haven't reacted:

And when I have reacted:

Personally I find Github's styling much more obvious.

The mouse hover states in Hall are also a bit weird too.