Leaving university degrees aside, probably one of the most significant indicators of development expertise would be StackOverflow reputation. It is in fact so good that companies pay a lot of money to search for potential job candidates on that platform.
I wonder how a generalized version of such an IT expertise reputation system could look like. I was thinking of a decentralized GitHub where each commit you do as a developer is linked to your identity. Based off this data, and some metrics about how your code is used in production or is otherwise useful to humanity, a reputation balance could be derived.
Such a reputation that is derived from actual code you write could also be a great way of attaching a weight to each pull request review. If, for example, your reputation balance indicates you have years worth of experience in programming video card drivers in the Linux repository, your vote to accept a PR in that niche should score higher than a vote from someone else. Especially nice for open source projects with no clear core developer team.
A possible problem I see in using only commits as input would be that we incentivice developers to write more code, which may lead to the software quality suffering.