@hi you can do that on most fediverse softwares to be fair (assuming the user has it enabled in their profile!)
It's typically $instance_url/@$username.rss
or $instance_url/@$username/feed.rss or
$instance_url/users/$username.rss

(I really wish there was a standard url though!)

Regardless, yes, it is very VERY cool - I use it to follow accounts of whom I'm not particularly interesting in interacting with, but still want to see what they're saying i.e. hardware manufacturers, comedians, music acts, venues, etc.
:-)