On the challenge of writing accurate source spans on Unicode source code: https://reedmullanix.com/posts/unicode-source-spans.html
Also (see footnotes) a fair number of LSP clients assume UTF-8 despite early versions of LSP mandating UTF-16!
Inline links are much more convenient than footnotes. However, they're more distracting. Unless I'm completely new to a topic ("for an overview of the field see [3]") it's better to read the whole article first.
Are there better UIs? Hide the links at first?