Anne: I have added the Weight Watchers tag to my own tag list
I've done the same. I've also added the ones I've suggested. 
I've also taken lately to adding the words Weight Watchers after recipe titles, just to make it easier for anyone searching.
That's a good idea. I do have some recipes marked that way for gluten-free, but not all of them.
Steve will probably have more to say on the subject, but I think if we get too hung up on adding tags, it will eventually be out of control.
Oh, I agree with you. That's why I only requested the ones dealing with the most common food allergies and food intolerances -- I feel those are important, just like the diabetic one, which is already on the list. Also, many food manufacturers are starting to add them to their labels.
I've also thought of another way to handle them, in order to keep the lists more manageable, and that's to allow appending subcategories to the main or core tags. For example, take the "Course/Dish" tag of "Desserts". You could append subcategories to it, thus: Desserts:Cakes, Desserts:Cookies, etc. "Desserts" would remain as the core tag, but the subs could be personalized.
Then the food allergy/intolerance thing could be handled under two core tags ("Food Allergy" and "Food Intolerance", since they're not quite the same), and the specific allergy or intolerance would be in the subcategory.
This could also be done for the specific diets that are around: Special Diets:Atkins, Special Diets:Weight Watchers, Special Diets:South Beach, etc.
The advantage of that would be that the core tag lists would stay manageable, yet people wanting to use their own tags could still have that.
Of course, the program would then have to be able to search for those subcategories as well as the core tags.
It's really nice to see you posting and making suggestions. Sometimes this place is just too darned quiet.
You may come to regret having made that comment. 