Here is a first question to start things up:

Why can't we use @mentions in SharePoint document libraries comments as we can in Lists? We use it to keep the exchanges on a list item in the same place and to be sure that people are informed and I was surprised to find out the it is not possible in libraries. A library is basically a list with a required field that is the file. By the way, comments should behave the same way for all file types. Office or not.

Mark-Kashman  Cathy_Dew