If you take such substances fortified from such sources then you're not a vegeterian, same way you're not if you eat gelatin (yes, gelatin, not gelatine - that's how it's spelt over here) or cheeses with rennit in them.
I avoid any form of animal-flesh\bone-containing ingestion. I take supplements having carefully checked the ingredients to ensure they don't have anything I don't want. I don't eat cheese unless I've checked the ingredients. I don't eat anything vaguely chewy without checking the ingredients. I know plenty of other people who do the same thing. It's called taking note of what you eat, and there's really nothing wrong with it.
Good for you. I just have veggo friends who do the same and claim their diet is more 'natural' than eating meat. What the...? That said I have a lot of reasonable vegetarian friends and I love veggo food (red lentil curry = awesome). They don't try to judge me for eating meat sometimes, though.
If you want to eat fortified foods, go ahead. The only problem with such an approach is that you have to make sure're getting enough of everything else you need. For that to be the case, you'd have to have fairly detailed biochem knowledge not just of the basic building blocks of life like amino acids, carbohydrates and proteins but of trace minerals like magnesium, etc.
Anyway, when you're talking about gelatin, etc., it's relatively easy to get non-animal versions. Vit B12, on the other hand, you cannot get from non-animal sources (bacteria count as animals so any purified version counts as from an animal source). You can't synthesise it either. There are non-meat versions, sure. But it's simply impossible to get that particular vitamin from anywhere else other than from an animal somewhere. By your strict definition above of what constitutes a vegetarian, no-one can legitimately claim to be a veggo unless you're forego Vit B12. Give that a crack and I can bet you'll get pretty sick pretty soon.
For mine, veggo's are far too dogmatic on issues like this when eventually there will be a conflict in your sources of food. Even if you do get some foods from animal sources, that shouldn't be the source of the mental anguish it is. I certainly don't judge. If the aim is to be healthy, food dogma works in oppositiion to that.
