It isn't just you, and indeed, the alignment examples make little sense with a proportional typeface.
I checked the CSS, and for some reason the code blocks use the exact same fonts as the rest of the text (albeit with a new font-family clause just for them).
Came here to say the same; really struggled to see the difference between before and after. :) I think I'll enjoy reading the comments here more.
(Quite liked SQL Prompt's auto formatter, but a shame so hideously expensive).
This doesn't help when talking about alignment.