As far as the other three things (caffeine, sugar, adrenaline) I think the argument is we have a better understanding and direct experience of those vs. dopamine. You can drink a cup of coffee and feel obviously caffeinated day-and-night difference from pre-coffee, but you cannot drink a cup of XYZ and feel obviously dopamined.
There are definitely some obvious commonalities among the feelings produced by dopaminergic drugs as well which are similar to the feelings I naturally experience when working on a big project.
FWIW the best way to get a feeling for what serotonin feels like is doing MDMA since it dumps massive amounts of serotonin out. It dumps plenty of dopamine too - it wouldn't be nearly as fun without that - but the unique "rolly" feeling is very attributable to serotonin.
Not advising people take MDMA just to figure out what serotonin feels like, but for those who have it's very helpful to sort of "recognize" what different neurotransmitters feel like
Adrenaline is one that is more common for me, and impossible to mistake. I can literally taste it.
Indeed, but I guess what I'm saying is that the feeling you experience isn't further evidence that it's serotonin.
Your connection between the feeling and it being serotonin is purely based on the studies that have been done. Those studies are the evidence. The qualitative feeling we get doesn't add to the body of evidence.
That is what the original author was arguing against. People arguing with her online saying "I feel a dopamine rush, therefore it's dopamine that I'm experiencing. You can't tell me it's some other neurotransmitter."