> or reaction has always been meant to run as root, and we should live with that ?

That's my point of view. I think it's cool if users can tweak their 
system so that reaction runs unprivileged.

But as a distribution, I'd say it's cleaner/easier to run reaction as 
root by default, so that It Works™ for every use case.

You never know what command users will run with reaction. For example, 
I've seen users use reaction to restart a service when its logs show a 
certain message that indicates it's running but in a buggy state.

NixOS maintainers have decided to make it run unprivileged by default 
but to make it easy to run as root: 
https://search.nixos.org/options?channel=26.05&query=reaction&type=options#show=option%253Aservices.reaction.runAsRoot

my 2cts on that :)