When using @ to mention a user, the first users that should be suggested should be those in the repo (BB-12564)

When I go to mention a user in the issue tracker in the body or in the comments I feel like the suggestive options should first show users in that Repo or users in that comment thread that begin with those characters instead of all users throughout the entire site. It would be extremely rare for someone to mention a user that they have never encountered on that repo in any info pertaining to the repo.

I'm sure this is a much bigger undertaking but my thought is that when suggesting users using @ the query first looks at repo users, then at commenters / issue owners on that thread, and THEN all users.

For instance, if I was typing "@Lin" in the comments section here, the first suggested user should be anyone assigned as a user in your repo that begins with "Lin" and then would suggest my user Lindsay AnnB and THEN all other users "@lin" as seen in the screen shot