That being said one claim here would be that allowing self-experimentation would pressure people into self experimenting due to how our academia and labs are structured these days i.e. a junior scientists could be pressured into self experimentation by their superiors. So this is definitely not as clear-cut as one might think.
As someone who suffered badly with ulcers in my teens I'm particularly grateful for his work. One course of antibiotics and I never had that problem again.
More so for him and his collaborator having dinner each year when the Nobel prizes were announced in anticipation of the call from the Nobel Prize Committee. Legends.
If people get rewarded for self experimentation, either directly with prices or indirectly with fame and success, more people will try do it. That certainly does raise ethical concerns. It worked out for people you mentioned but there will be many others who might harm themselves doing it.
In the case of self-testing it raises concerns of objectivity, not just in terms of perception and observation but with regards to bias and intent, throwing into question the results and reasons for the study.