The question of re-posting bad reviews came up in an author group discussion and my immediate answer was why would you re-post a bad review? When promoting your work, always highlight the positive, never the negative.
That said, even a bad review will have some kernel that can be used to promote your work. That’s where ellipses come in handy. You quote the good, forget the bad, and move on. There’s no rule that says you have to tell people that the review you’re quoting was two stars (or below). And even if you link to the full review, very few people will click the link to read the rest.
When quoting the good, don’t put words in the reviewer’s mouth. Don’t splice a sentence together of all the good parts. Some bad reviews won’t have anything worth quoting. Likewise, some good reviews have nothing quotable either. It happens. Chalk it up as a loss. Think of it as free advertising (most review sites display the book cover and link to the buy page) and remember the review is one person’s opinion.
When I debuted, the authors of my first pub gave tons of really good advice. Several things have stuck with me over the years. One of those is a very simple fact that I’ve found to be true the more books I release — Readers very rarely read the book you wrote.
Everyone brings their own baggage and expectations to a story. What the author sees as heroic, the reader might see as brutish and overbearing. What the author sees as a joke, a reader might see as an insult. All that colors a person’s perception of the story and later their review.