My understanding is that the anonymous profile thing won't really work. That's as far as ActivityPub is concerned - one of the protocols behind Lemmy, Mastodon et al.

Every person/bot/whatever which comments, posts, upvotes; any social "activity" must have an independently verifiable public identity (via WebFinger). Here are some example identities:

• my Mastodon account: otl@hachyderm.io
• a random kbin account: density@kbin.social

When some "activity" is performed by that identity, a message is delivered to many (many!) servers. They could be running anything but we commonly see Mastodon, Lemmy, Meta's Threads (soon?).

Each server can really do whatever it wants with that message. For example:

1. I posted this photo from a Mastodon instance (via @otl@hachyderm.io)
2. The Mastodon server also delivered a message to !motorcycles@lemmy.world.
3. The Lemmy server at lemmy.world stored it in a big database so subscribers can read it.
4. @ganksy@lemmy.world replied "Wild and chilling landscape".
5. Lemmy stored the reply and also delivered the reply to @otl@hachyderm.io.
6. Mastodon stored the reply in its own big database so I can read it.

Coming back to the OP:

That was a long winded way of saying we should have (optionally) private profiles in lemmy.

Here is some service's idea of what @otl@hachyderm.io is:

• kbin
• lemmy.sdf.org
• Threads: https://threads.net/@otl@hachyderm.io (not yet!)

There's no way to make a profile private because there isn't really a profile to begin with. What we really have is just the activity received from @otl@hachyderm.io. The whole thing feels a lot more like email than popular social networking sites when you get down to the nuts and bolts.

Old-school mailing lists archives also offer a way to search for posts by author. e.g. Richard Miller