Sending email to bugreport@ doesn't reply back with the task #, so I and all users on the email have to go search for the bug.
I'm cc'ed on hundreds of bugs. The workflow I'm thinking about is forwarding a feedback email to create a task, everyone who is cc'ed can't jump in and comment, either by clicking through or replying to the email. They have to go into maniphest and search for the bug (which may not be created yet, there's a delay), or maybe they'll get a cc email, but it'll have a different subject line that they can't star before it arrives. Simply, filing a maniphest task by email creates a thread that is left dangling when it could be a useful reference.