Alasdair Taylor's Answer

The only potential legal issue I can see here is copyright.

If a person has provided a written comment to you, and that comment is non-trivial and “original”, then what they have written may be protected by copyright as a literary work. If you copy a “substantial part” of the comment without permission, then in theory that could amount to copyright infringement.

The quoted phrases have a special meaning in copyright law. The “originality” hurdle is low, but nonetheless something like “Your customer service is great!” would not surmount it, and therefore would not be protected by copyright. A longer piece of text, for example this answer, probably would be original in the copyright sense, and probably would attract attention.

Again, if you took only a commonplace phrase from the comment, then that would not usually amount to copying a substantial part.  E.g. taking “Your customer service is great” from a longer text.

Of course, while people do sometimes get into disputes about testimonial comments and copyright, these sorts of things do not usually get anywhere near a courtroom.

A non-legal point: why not get permission to use individual names and company names?  Testimonials are much more persuasive if they are given by someone identifiable.