In DLP 15.8 when you paste an entire paragraph in the Keyword policy "Match any Keyword" text field the rule fails if the paragraph exceeds the width of the text field.
You can save the rule, but it will not detect the keyword paragraph.
If you limit the keyword or keyphrase to the width of the text box the policy rule does work, that character string is detected.
In 15.8 the individual keyword or keyphrase is limited to the width of the text box.
So if you paste a paragraph larger than the width of the text box, that keyword/keyphrase will not work.
In 16.x you can paste a paragraph larger than the width of the text box and the rule will work.
Currently, there are no plans to update 15.8 to work the same as 16.x.