I think that the absolute worst type of quote to come across when practicing my typing is one that uses commas inconsistently. For example, when coming across a list that is short, concise, and compact, I'd like to be able to speed through it without stopping, erasing and starting again because I like an Oxford comma and somebody else does not.
I might be the only one who might have noticed but this passage has an example where the Harvard comma is used and then it doesn't. I prefer the Harvard comma too, but I really just prefer consistency. :)