In this case it is because the posting account has explicitly ticked 'Ask apps and sites not to show my account to logged-out users'. Of course, Bluesky is built upon the open AT Protocol, so you can still view the post by any one of a number of other means without requiring a complex workaround.
Need login to view this, is there nitter for bsky posts?
That Bluesky link is sign-in-walled.
Ironic, given how many people criticise X.com for its sign-in requirements.
In this case it is because the posting account has explicitly ticked 'Ask apps and sites not to show my account to logged-out users'. Of course, Bluesky is built upon the open AT Protocol, so you can still view the post by any one of a number of other means without requiring a complex workaround.