The comment length is limited to 600 characters, but if your feedback is longer then you can consolidate into posts; Make your feedback (full length) in a post or by starting a new topic about the case and drag a link in the feedback comment field.
Theymos suggested this earlier :
For feedback longer than the 600 characters, I prefer that you consolidate it into posts somewhere. Even if the comments are good, long comments kind of monopolize the page.
If anyone runs into it and thinks that they should be allowed to continue, PM me and I'll think about the issue more. I could whitelist certain individuals, or I could make it expand significantly at higher ranks.
I find it's so much easier and doesn't need to be discussed more, as a feedback is not a telling-story when you can provide evidences in reference link.