There is nothing to fix: code blocks do (almost) exactly the right thing for code. (the indentation on the right is unnecessary and counterproductive, though, but that's not the main source of the complaint here.)
They are horrible for quotes, especially on mobile, but that's not what they are for. Admittedly, quotes are vastly more common than code on HN and HN could use a good quote formatting mechanism, but that's a missing feature, not a bug in code formatting.
There is nothing to fix: code blocks do (almost) exactly the right thing for code. (the indentation on the right is unnecessary and counterproductive, though, but that's not the main source of the complaint here.)
They are horrible for quotes, especially on mobile, but that's not what they are for. Admittedly, quotes are vastly more common than code on HN and HN could use a good quote formatting mechanism, but that's a missing feature, not a bug in code formatting.