"Widgets display content sans wpautop formatting" since version 2.2.8.
This means the basic output is a continuous block of testimonial text which is quite often difficult to read and not pleasant to look at.
Inserting p tags into the testimonials' code does not work for me; for some reason they are not rendered visually in the widget. Alternatively, br tags do the trick but they are deleted every time the editing screen is switched from "HTML" to "Visual".
This process is ultimately manageable for a proficient user but one with relatively basic skills would find it too complicated.
Therefore I propose an optional wpautop functionality that would be turned off by default, but those who need it could turn it on.