The examples below are written to show the pattern. They are not real customers or real quotes; every one is labelled as illustrative so nothing here can be mistaken for a claim.
Illustrative, weak: "Amazing tool, our whole team loves it! Five stars." Attributed to "J., marketing." Nothing here could not have been typed by the company: no result, no person, no context, and the exclamation mark is doing the work the evidence should.
Illustrative, strong: "We used to rebuild the client report by hand every Friday and it ate most of the afternoon. Now I export it in a few minutes and spend the time on the actual client call." Attributed to a named account manager at a small agency, with a photo. Same product, same enthusiasm, but it reads as a memory of a specific Friday, and the visitor who also loses Fridays to reports recognises themselves. The difference is not length or polish; it is whether a specific human and a specific outcome are present. The same applies to logos: a strip of company names asserts nothing, while a two-sentence case under one logo, said by a named person there, is a claim with a witness.
Where the quote sits matters as much as what it says. A testimonial works at the moment of doubt, which happens next to the button, not in a section titled "What our customers say" three screens down. The visitor reading the headline is asking "is this real?"; one specific quote beside the hero call to action answers it. The visitor at the pricing block is asking "is this worth it?"; a quote about the result it paid for answers that. The visitor at the form is asking "what happens after I submit?"; a quote about the first week answers that. A dedicated testimonials section still has a place on long pages as depth proof, but it is the supplement, not the strategy.
Carousels are the worst placement of all: they hide most of the quotes most of the time, auto-advance before anyone finishes reading, and signal that the quotes are decoration rather than evidence. If you have three strong quotes, show three. If you have one, show one, beside the button, and go collect more.