I have blocked an instance in my profile settings, which seems to block posts. However the instance’s user-comments still come through and are still visible and they react to my comments.
I blocked a few users from that instance which makes the comments disappear, but how can I block all users?
Lemmy doesn’t allow that kind of block. You have to use a Piefed instance such at https://piefed.world/ (same team than Lemmy.world)
You can export and import your settings
Instance blocking is just blocking all communities on that instance, unfortunately.
Like Blaze said, you can try Piefed (LW also operates a Piefed instance) or you can use an alternate UI for Lemmy that does hide users from blocked instances. Not sure which do except Tesseract (https://t.lemmy.world/) since I wanted to be able to do the same thing.
The setting for that is under Settings -> Filtering -> Hide Users From Blocked Instances
