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:
ServerName jenkins.example.org # change to actual server name
RewriteRule /asynchPeople/ - [F]
RewriteRule /people/ - [F]
ProxyPass / http: ProxyPassReverse / http: ProxyRequests Off
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
This should keep at least most of the users out, even if it's likely not a 100% solution.