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The EPIC docs confirm that this is working as intended - there is no support for Eclipse Tasks View priority levels.
It looks like task priority was implemented in Galileo (Eclipse v3.5) and EPIC never got around to adding the extra Tasks View functionality to its configs.
Any differentiation between comment types has to be configured within the Tasks View. All EPIC does is find task tags specified in its configs and sends their associated text (description) to Eclipse's Tasks View as a basic Eclipse Task object of normal priority.
From this point it is possible to filter by keywords in the description attribute of the Task, as in my workaround example above.
I was intending to use the priority attribute to specify the scope of the task. In order to simulate this behavior I created more Tasks View configurations with different description keywords which correspond to different scoping display rules. It's a little bit of a pain and it requires me to do more typing (room for error) in my keywords, but it works.
I also recommend creating a couple of Tasks View configs which ought to be in Eclipse by default - file and project scope views. To do this create a new config with no filter (so that it will catch all tasks EPIC passes) and change the scope setting to either "on selected element only" or "on any element in same project" respectively for file and project filtering. Make sure that "Show items that match any" is selected but be aware that this means that if you were to select both File and Project views it will display the least strict config - Project. I prefer this setting so that I can look at multiple different task tags in one view, but since you can create as many Tasks Views as you like it's entirely up to the user.
Anyway, hope this helps anyone out there to bring a little order to their workflow using Eclipse and EPIC's tasks integration.
Strange things are afoot at the Circle-K.