Not sure if this is a bug, or if the feature is working correctly, but blocking the instance on the shown post blocks mastodon.uno instead of feddit.it which is what I would expect.
It would be helpful if the block options in the menu showed the name of what they were going to block, as I've often accidentally blocked the user's instance instead of the community's instance in a post. It's difficult to know at a glance what the different parts of a post's categories are (user@instance/community@instance, etc).
Also, blocking an instance means comments from users of that instance are blocked too, which is not desirable. I think the point of blocking an instance is only to block posts from communities on that instance.
Thanks!