Do you think it is possible that developers are paid more equally around the globe?No, I am skeptical of that. Each location has external factors such as cost of living and supply and demand that will not allow a global uniform rate to be set.
What if developers are being paid based on hard- and soft skills only while not considering the avg local salary payments?
There is more to it that strictly programming skills which are notoriously difficult to judge/measure. There are time zones and language proficiencies and cultural pressures and expectations. That is just the tip of the ice burg and assumes that a manager is even capable of managing a remote team of freelancers. In my experience very few actually are.
I'll give you a real personal example. We have several teams of predominantly South Asian devs who chronically and wildly over promise and under deliver. This so prevalent, I now (perhaps in a racist way) assume that this is culturally ingrained and is not malicious at all but a way to save or gain face. After years of working with these teams I know "I fixed the issue and it is impossible that something like this will happen again" does not mean to me what it does to the devs making these statements.
Additionally, if this was indeed the only (and somehow perfect) criteria, supply and demand would dictate that a global race to the bottom and rise in worker exploitation and nation-state gaming would occur as happened with many forms of manufacturing.
Imagine a developer in Finland being paid the same as one in Romania or the US.
If they got paid the same as a Romanian, then they would either be daft and live in poverty or be constantly looking for a job with appropriate regional pay. I don't know how Finnish pay compares to U.S. pay. I'm sure that in some regions the results would be that they were wildly overcompensated but that would be true if I paid a dev in Scranton PA the going rate for one in Palo Alto.
What's your take on this HN? Would you use a 'skill-appraisal' service that tries to accomplish that?
No, never. If I wanted to know what my going rate was I would start with Stack Overflow's survey. It seems to be in the general ballpark for the U.S. and can be negotiated from there (particularly with respect to cost of living)