If you have a way to inject CSS into a page, via a browser extension or other method - here is the code I've just put together for Arc's 'Boost' feature, to make the favourites and boosts a bit smaller.
After all, you wrote the post in the first place, you don't need to see the whole content each time someone likes or boosts it!
It seems to need all those !importants in there on Arc, other methods may not need these.
Edit: These have changed! Made the code smaller, by a little: