Merge pull request OAI#1090 from OAI/issue-1078

Permit tooling to limit commonmark usage

Author: darrelmiller

versions/3.0.md

@@ -168,7 +168,7 @@ password | `string` | `password` | Used to hint UIs the input needs to be obscur
 
 ### <a name="richText"></a>Rich Text Formatting
 Throughout the specification `description` fields are noted as supporting CommonMark markdown formatting.
-OpenAPI compliant tooling MUST support [CommonMark 0.27](http://spec.commonmark.org/0.27/). 
+Where OpenAPI tooling renders rich text it MUST support, at a minimum, markdown syntax as described by [CommonMark 0.27](http://spec.commonmark.org/0.27/). Tooling MAY choose to ignore some CommonMark features to address security concerns. 
 
 ### <a name="relativeReferences"></a>Relative References in URLs