Avoid using “this,” “these,” etc. by themselves (as pronouns); your sentences will be clearer if you follow them with a noun.
I'm deleting virtually all exclamation points.
Avoid using ampersands, even when space is tight.
Any questions about my “remarks”? The first one was about heading structure; I recommend reviewing the other chapters for the same issue. (This was in regards to Chapter 1.)
My first impulse was to start doing away with italics, but I stopped because it looked like you're using them in an expanded application of O'Reilly style for first mention of technical terms - you're using them for everyday terms and names in a social media context (see below). Still not sure you need them, though; it might get a little old by Chapter 6.
Here are my style notes so far:
<eBay seller's> Feedback score
explicit reputation statement
global reputation
italics: use not only to introduce technical terms but to introduce known terms, names, or categories in the context of social media
Many figures in this chapter are diagrams without captions. I think that's OK for these figures, but I think the meaning of the diagrams could be clearer; consider adding callouts and more explanation in the text.
Overall, italics and caps are used too much to be effective in highlighting things, so in this chapter I took out a lot of italics and lowercased a lot of capitalized words. Most of the time this worked - i.e., the terms were actually easier to grasp without the extra italics and caps treatment - but in a few cases I had to change the wording, e.g., “the <i>Helpful</i> claim” didn't work as “the helpful claim,” so I changed it to “the was-this-helpful claim.”
Are you planning to include a glossary? If you are that would be a really, really good thing.
Please see additions and changes to attached stylesheet, including the last section on overall changes.