It would be great to allow @mentions in features. I could see this being useful in:
For me this is a priority because otherwise it's hard to call attention to a feature to someone unless you make them a watcher. But, they may not be be a watcher, they may need to just address one comment. It's pretty important to us, we got spoiled with this using Pivotal Tracker and Trello.
|Release time frame|
This will be coming soon as part of an updated text editor. We want it too!