I don't imagine there's any actual research into this but if there is - brilliant! But, anecdotal experiences would be very useful.
Have you yourself, or have you supported someone who has had hyperemesis in one pregnancy, then gone on to have another pregnancy while breastfeeding?
If so, was the second pregnancy any different (from a HG point of view)?
I'm just thinking that as BFing can reduce "normal" morning sickness, can it affect HG?