Yep, same here.I can see your bolding. I don't think it is a Brave problem. I use Brave and can see when I make text bold or italic, as soon as I type here.
I have them both, too, and for me Brave is better as I can't get a toolbar to come up on Vivaldi. Plus, it's a bit too complicated for me as I'm not that computer savvy.Use Vivaldi, I have both Vivaldi and Brave and after trying both, I now use Vivaldi.