And why are you commenting about medical issues if you're not qualified?

I don't agree with this sentiment and this exact view is what killed amateurship in the intellectual fields. Apply the same reasoning to every single qualifiable topic and this becomes ridiculous.

You should be able to comment on whatever topic you want, and your comments should be judged on their own merit, irrespective of your status or perceived authority on the topic.

That isn't saying that we shouldn't value the qualified opinion, it is undoubtedly the case that they possess more knowledge and likely more merit in their comments than the layman, but gatekeeping the discussion of a topic by an individuals formal qualification is reticent and a pointless inhibitor of heterogeneity.