I don't think it's impossible, I think it's a lot of work though. Especially for one person, it would take the right person. I could see someone like Walter Bright doing it (he created D originally by himself and other compilers).
I don't think I have the energy to do the entire DOM myself, and implement a JS engine, and CSS, and so on... Plus all the nuance of image rendering (even if you use third party libraries for this, you gotta figure out which ones to use and ensure you're doing so correctly and securely).
Set a lower standard though? HN is arguably a good website with just enough of each tech and high signal to noise ratio. How difficult to make it work in a new browser? Who cares if it renders the Facebook wall misaligned.
I don't think I have the energy to do the entire DOM myself, and implement a JS engine, and CSS, and so on... Plus all the nuance of image rendering (even if you use third party libraries for this, you gotta figure out which ones to use and ensure you're doing so correctly and securely).