currently, only the xml output properly escapes suggestions' fields. I've seen problems with the "text" and "formatted_text" attributes, but it might extend to "title" and others. the values contain unescaped newlines and double quotes. examples:

"text":"ZenRep pro tip #1: \n

and

"formatted_text":"\u003Cdiv class="typeset"\u003E\u00
(class="typeset" being the problematic part)

this applies at least to the responses sent by /api/v1/suggestions.json and /api/v1/forums/{forum_id}/suggestions.json