That's on the client, not the protocol. A few folks have built clients but for some reason hasn't made this a feature.

All posts are publicly accessible though -- here's Jake Tapper's posts for example

https://bsky.social/xrpc/com.atproto.repo.listRecords?repo=d...

EDIT: This client lets you look up any post/profile without logging in https://blue.amazingca.dev/?username=did%3Aplc%3Aupkgvxvhn4e...