Currently, our uses do not have the Browse Users permission - we don't give them this because we have multiple clients in our system and we don't want them to see each other's issues.
Instead of using @ mentions, isn't it possible to use wiki markup if you know the person's username? Say my username is achristensen - the wiki markup is [~achristensen].
I swear this worked in JIRA 6.4, but our users are reporting that this doesn't work, and I can confirm in my own testing in JIRA 7 that the wiki markup doesn't seem to initiate an email notification. Did this change in JIRA 7? Is the Browse Users permission now required to even send a notfication email for a wiki markup mention?