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/). 
+OpenAPI compliant tooling MUST support markdown that is compliant with [CommonMark 0.27](http://spec.commonmark.org/0.27/). Tooling MAY limit some CommonMark features to address security concerns. 
 
 ### <a name="relativeReferences"></a>Relative References in URLs