Possible workaround: Hide Jenkins behind a reverse proxy (e.g. Apache). Configure it to listen only on the 127.0.0.1 interface (--httpListenAddress=127.0.0.1). Forbid access to people/asynchPeople URLs. Those links will then result in 403 Forbidden.
Sample Apache httpd.conf excerpt, assuming reverse proxy and Jenkins are running on the same host, Jenkins on port 8080, Apache on port 80:
<VirtualHost *:80>
RewriteEngine On
ServerName jenkins.example.org # change to actual server name
RewriteRule /asynchPeople/ - [F]
RewriteRule /people/ - [F]
ProxyPass / http: ProxyPassReverse / http: ProxyRequests Off
</VirtualHost>
Of course, this simple pattern will prohibit access to e.g. the job named 'people' as well. Haven't tested this with all possible Jenkins URLs, making sure it works for those is left as an exercise to the reader ![](/images/icons/emoticons/smile.png)
This should keep at least most of the users out, even if it's likely not a 100% solution.
Without permission to view people, other views that can also be used to list people known to Jenkins should be restricted as well, like 'Changes' (remove author information?).
Maybe even information such as the field about who created a slave? Who started a build?
There's little there can be done for change lists sent via email-ext though. Other plugins might also provide ways to circumvent restrictions.