For now! The bluesky URL contains "itch.io" (their handle), and under atproto, DNS name resolution is actually an integral part of handle resolution. It will start 404ing if/when relevant caches expire.
I think GP comment meant that when you link to a Twitter thread, logged-out users will only see the single post without any replies. On Bluesky, you can see the whole thread.
This one uses the "DID", not the handle, and will not 404: https://bsky.app/profile/did:plc:oy37ivqnriw6nx3lrbcht2u3/po... (cc dang)
Open issue regarding making bsky URLs less fragile while also not looking ugly: https://github.com/bluesky-social/social-app/issues/1221