Well I've debunked something a MCHN told me when DS was 2 months old. I was using nipple shields to breastfeed, and she told me outright that my milk would dry up if I kept using them... now here we are, DS is now 20 months and we are still breastfeeding using nipple shields! I don't even think anything of it now, I'm so used to them that I forget it's not 'normal' most of the time!

More recently, I think the main b/f myths I've debunked have been related to breastfeeding while pregnant. I've shocked a few people telling them I was still breastfeeding (and breastfeeding quite a lot) when I fell pregnant. A lot of people assume you have to wean in order to fall pregnant - I know some women do, but not everyone .
Also, I've come across who thought you couldn't breastfeed while pregnant - I think they thought it was either bad for the developing baby, or that your milk dries up. So far so good here though!