Oh. I just learned by accident that I can drop the URL of a post somewhere in the fediverse into the search box on my #Mastodon instance, and then it gets pulled down so I can write a reply.
@sydneyfalk Judging from the number of boosts of that post in my Notifications stream, I wasn't the only one who didn't know up to now.
I have to admit I didn't really read much of the user documentation yet, so I should probably check if that function is mentioned somewhere...