My initial reaction is that this could quickly get confusing as you wouldn't see all of the selected articles. What operation do you want to perform on the selected articles?
Regarding operations, my initial thought would be for archiving or deleting purposes. It may be more of a reflection on how I think, but if I’m archiving recipes, I can be selecting something under the “Chickpea” tag and be reminded when I see the “Lamb” tag that I have some recipes that I would like to archive there as well. Of course, this works best when you already know your actions. To reduce confusion, you can have a “Selection Filter”, so you can see everything you selected. Selecting articles under different tags can also be supplemented by a number, indicating the number of articles selected, to the right of the tag. This would allow selections to be done in one operation, though it could detract from the elegance of your design.
Thanks for the extra info. I think this is something that needs to stew for a while and see what other contributions are offered.