Having comma in username creates problem when user is added to a watch/group list

Steps:
1. Create a user name having comma in it.
2. Now try to add the user in watch list or try to add the user to any group.

Result:
1. JIRA give error message.
2. Due to the comma in name, the user name is treated as two names and hence it failed when user try to add them in list.

Expected:
1. A better handling is required. Either the user name having comma is handled or we should not allow these in username