The quoting system in xenforo is excellent and enhances readability with features like 'click to expand' etc. but as with any quoting system, it does lead to duplicate content and increase in the bulk of content on a page.
For instance, if there is a post of 1000 words and a couple users quote that, the bulk of unwanted content on the page increases hugely. This is also not good from the search engine optimization perspective as it leads to content duplication. My suggestion would be to have a quote system that auto minimizes quotes.
As an example, if someone where to quote the above message, the quote system will only post the first few lines and the last few lines instead of the whole passage.
Ex: "hello, the quoting system in xenforo is excellent.... system that auto minimizes quotes."
This way anyone who wants to read the original message of the quote can always click the permalink. I think this will increase readability hugely, make lighter pages which will load faster and also be search engine friendly. Of-course this would be an optional thing.
Btw, I wonder if there is an addon out there that can do this. Would be more than happy to buy it.