I'm sure you know much more about this than I do. I honestly don't know a great deal professionally about prolonged bf, it really doesn't come up that often, you obviously have done much more research than I have.
My post was actually quoting someone who mentioned seeing bottle feeding (on a toddler) as a comfort method as something that was ok, and I wanted to make a point that it really is not. I know you agree with me on this. I know you are right when it comes to the different mouth positions and how the milk goes straight down with bf, however, as a health visitor I know this doesn't automatically happen with an older breast feeder, as they will be doing what toddlers do eg not concentrating on feeding. In theory I know you are right, but in practice there are times the milk does pool. I may be wrong on this (not looked into this) but I'm not 100% convinced that breast milk is good for the teeth, particularly as you say, when in contact with other foodstuffs. It is unlikely a child will be able to brush there teeth when out and about and snacking. I'm not saying you shouldn't extend breastfeeding or that breastfeeding shoud'nt be done in public.
You are right about fruit being bad for the teeth, I actually meant that if you are going to give a child a snack because they are hungry, you may as well use the opportunity to provide something much more nutricious than milk (yes I know milk is nutricious, but most of the time, the child will have their full requirement of dairy and will need to meet their requirement in other areas), as you were going to cause an attack on the teeth anyway by giving milk.
Also when I mentioned dummies, I was talking as an alternative to a comforter in regards to milk pooling in the mouth. There is no doubt that a dummy would be better in this circumstance, however if the child has only used a nipple/teat as a comfort source, by the time they are a toddler, there is not much point starting thumb/dummy. I completely agree that both the dummy/thumb cause problems of their own, but if a child is already doing one of these, there is no point adding to them by encouraging the potential for rotting teeth. If a toddler (lets say a bottlefed toddler for this arguments sake) wants the comfort of sucking, not for hunger, I would suggest encouraging the child not to suck from a bottle but to use a dummy/thumb if they are used to that. Not only does drinking milk for comfort lead to rotting, it can also fill the child up leaving no room or appetite for other valuable nutrients. You'll be surprised how many parents have a nightmare at the dinner table and claim there child is picky eater. Quite often when the family is suported in weaning the child off of milk as a comfort, the dinner time becomes a much easier and fun experience. If the child is already using thumb/dummy you may as well use them to eliminate some crisis' when you are going to have the crisis of weaning them off the thumb/dummy anyway