I'm experiencing this in Confluence server 6.15.2.  It's using JIRA's user directory, which is linked to AD.  Anonymous viewing is enabled.  The user in question is visible under User management->Find user, but not from the Share widget on any page.

Is this fixed in newer versions? We're planning an upgrade anyway.

We have the same problem and the workaround to visit the users profile from those users which are not found or to perform a reindex, is not a workaround.
We use jira as user directory.

The requirement that i have is that new users will be found immediately after i creat them. Even the never logged in to confluence.

Daniel Varela Santoalla added a comment - 13/Aug/12 4:30 PM
Found the same problem. The workaround works for me too. But it is a bit unintuitive, is it? You would like to share things even with users that have never logged in. They will log in if you invite them, but I can't!

--> absolutely right

Evan Goldin added a comment - 20/Mar/13 8:41 PM
This is really annoying and hurting adoption of Confluence and Jira at my company. Here's what happens:

1. People use an @mention to tag someone
2. Get confused when they're not availabine in the drop down list
3. Talk to the user, user says "Oh yeah, I don't have a Jira account"
4. That first person talks to me, I get them a Jira account
5. The person trying to tag them with @mention tries again, only to see they're still not available
6. That person talks to me again, where I go in and see they've never logged in
7. I tell both of them "Please have Jerry, etc. log in to Jira. Once he does, you can tag him."

The whole thing is very confusing and frustrating for new users.

--> i confirm

This is really annoying and hurting adoption of Confluence and Jira at my company. Here's what happens:

1. People use an @mention to tag someone
2. Get confused when they're not availabine in the drop down list
3. Talk to the user, user says "Oh yeah, I don't have a Jira account"
4. That first person talks to me, I get them a Jira account
5. The person trying to tag them with @mention tries again, only to see they're still not available
6. That person talks to me again, where I go in and see they've never logged in
7. I tell both of them "Please have Jerry, etc. log in to Jira. Once he does, you can tag him."

The whole thing is very confusing and frustrating for new users.

Found the same problem. The workaround works for me too. But it is a bit unintuitive, is it? You would like to share things even with users that have never logged in. They will log in if you invite them, but I can't!

Thanks very much it works now. I appreciate the feedback.

Users in the 'share' list comes from the search index, however users in the user list comes from the DB/External LDAP. This means that if you use an external user management like LDAP and mr Trelean has not yet logged in (he will be added to the index the first time he logs in. Users created in Confluence will be added when they are created) he will not appear in the share drop down.

See attachments - I cannot share the username, but he appears in the list of users

I have noticed the user is in the user list however not in the People directory - what is the relationship there?

Can you share the username? I know there were work done as users with repeated n-grams (sub-strings) did not show up. If that is the case it is likely it is fixed already, but I can not determine that from the report.