In-comment mentions errors

There are several behaviours with the in-comment mentions that would appear to be bugs:

1. Allows any user to mention by entering manual WML <username> when the user does not have the appropriate permissions (e.g.: browse projects, browse users). However, It does not bring up the search box if using @username if that user doesn't have permissions.
   • Please see Error1 and Error1_Preview. User "testnull" is not a member of any groups.
2. Certain cases of mention syntaxs do not work as expected:
   works:

   [~dcurrie@atlassian.com]
   

   dcurrie@atlassian.com
   does not work:
   [@dcurrie@atlassian.com]
   @dcurrie@atlassian.com
   [@~dcurrie@atlassian.com]

3. When mouse clicking on a user, as in Error3a, the Found no matching users prompt will appear, as in Error3b. This does not appear if you use the keyboard. To recreate:
   1. Open comment.
   2. Mention @<user>.
   3. Mouse click on the user.
   4. Press space and the prompt appears.
4. A user without required permissions can mention a user with required permissions and it will notify them. For example:
   • Testuser is in jira-users.
   • Testdeveloper is in jira-developers.
   • Browse Users for the project is jira-developers.
   • Testuser mentions testdeveloper using testdeveloper.
   • Testdeveloper receives notification.
5. Using the above example permissions, when Browse Users is set to jira-developers and I am logged in as a User without that group, I can still click the hyperlink for the mentioned user.