Should I add comments (even if the work hasn't been completed) to notify the issuer of changes?
Whenever something new happens regarding an open ticket, this information is added to the ticket either by replying to an email that you got from the ticket, or by logging into Gnosio and clicking on the ticket, and then clicking on "adding a comment." If everyone adds new information as a tickets progresses, then you will be able to help customers who call wanting the latest information. Eventually, they won't even call -- they will be the ones who start the ticket and they will look at the web site to know the status. How much time will you save when you won't have to listen to excessive verbial abuses over the phone any more? That's why it's important that everyone logs updates to tickets as they happen.
To answer your question about who gets notified, all the details about who gets notified are
here.