> A nice thing is that outlook can simply sum up the reactions and show them along the message in a non-intrusive way.

Yeah, that's why I came to like the feature. It's even visible at two places: in the thread list and on an individual email.

The only downside for now: the choice of emoji is too limited. I want my eggplant emoji! But given the history in Teams, where they started with a limited set of emojis, before adding all of them and finally allowing custom ones, I guess it's coming!