Please don't: when used for code, preserving lines (even when requiring scrolling on mobile) is a good thing. 100% width is fine, no reason it needs to be as narrow as it is.
If a blockquote format is desired, that's great, but don't change the code formatting to make it a slightly-less bad (but still horrible, because of monospacing) way of presenting blockquotes.
I'm given to understand changes may be in the offing, though whether or not this specifically is addressed, I'm not sure.
On desktop browsers with extension support, you can use Stylus to fix this specific annoyance by setting "pre-wrap: word".
And yes, blockquote support would be hugely appreciated.
FYI: https://lobste.rs offers full Markdown for comments.