First: I'm not sure of the exact origins of things. The way I see it, academic markdown is more of an ecosystem of tools with a lot of overlap. There is no one single markdown workflow right now when you want to do do academic writing. I think this is because no one is sure what the final spec should look like and people are trying things out and seeing what sticks. I feel that there has been some convergence in the last 2/3 years though.
There isn't a PR for internal referencing yet because the implementation hasn't been worked out yet and it isn't a simple change (should there be a native representation, should it be a filter, which syntax should we use, what about the existing citation syntax...).
Second: The PR for image attributes is here: https://github.com/jgm/pandoc/pull/1806
There isn't a PR for internal referencing yet because the implementation hasn't been worked out yet and it isn't a simple change (should there be a native representation, should it be a filter, which syntax should we use, what about the existing citation syntax...).