Event frame notifications combined with PI Vision event frame table almost provides the features you are looking for. Event Frame table contains acknowledge (PI Vision 2017) and you an add comments +attachments and acknowledge. Notifications can be set to escalation for multiple reminders based on event frame trigger time.
I would have to understand more about the workflow and what type of changes you need but can offer a few starting points. Do you need to only detect EF starts or do you new to update with the EF end as well? Is the responder actually commenting on the EF record or into another database?
One way to get all of the changes would be to use FindChangedItems in the AF SDK (this will be your listener) and there are a lot of code samples on PI Square. You can use this to figure out which EF are new and which were modified. You can refresh and obtain the latest change. Unfortunately, AF SDK does not provide what has changed on the object, rather it has been changed. AFDatabase.FindChangedItems Method (AFIdentity, Boolean, Int32, Object, Object) You probably only want a subset of EF so you can use the IsMatch method of AFEventFrameSearch to filter the results.
An alternative to all of this is to perform a search using AFEventFrameSearch Class: AFEventFrameSearch Class to find all the event frames.
You can specify the AnalysisID as a filter in the AFEventFrameSearch. So you could find any open event frames from the analysis or event frames from that analysis that occur within a time range. Periodically polling the search every few seconds can provide updates that should be adequate for a UI application.