clarifications thanks to @annevk, @bkardell and @otherdanial

Author: polx

mathml-safe-list.md

@@ -4,9 +4,10 @@
 MathML-core considers all elements and attributes of MathML-core (as listed in [section 2.1 of MathML-core](https://w3c.github.io/mathml-core/#mathml-elements-and-attributes)) as safe and not needing a sanitziation except the following elements.
 
 We recommend the [Sanitzer API](https://wicg.github.io/sanitizer-api/) to sanitize MathML by keeping all elements and attributes except the follwing:
-- any common attribute with HTML attributes which need a sanitzation,
-- the `maction` and `mphantom` elements (the element can be replaced by their first child), and
-- any `annotation` or `annotation-xml` element whose `encoding` attribute is of a media-type that is is either absent or is not among the trusted types or if it contains an `href` attribute.
+- any common attribute with HTML attributes for which need a sanitzation as done in HTML,
+- the `mphantom` element which should be removed,
+- the `maction`  elements which should, ideally, be replaced by its first child element, and
+- any `annotation` or `annotation-xml` element whose `encoding` attribute is of a media-type that is is either absent or is not among the trusted types or if it contains an `href` attribute, which should be removed.
 
 ### Detailed Version
 MathML-core considers the following elements and attributes of MathML-core as safe and not needing sanitization:
@@ -20,7 +21,7 @@ Attributes of MathML-core:
 Moreover, the following attributes have their syntax and semantics specified in the HTML specification. The sanitizer behaviour on these attributes should be as is done on HTML elements: `on*, id, class, style, data-*, autofocus, nonce,tabindex` (for example any javascript should be removed).
 
 The elements of MathML-core which need treatment by the sanitizers are the following:
-- `annotation` and `annotation-xml` if their `encoding` attribute is not considered of a safe type (e.g. if the encoding is `text/plain` then it could be kept). If removed, the element should be replaced by its first child.
-- `maction` is replaced by their first child
-- `mphantom` is removed
+- `annotation` and `annotation-xml` if their `encoding` attribute is not considered of a safe type (e.g. if the encoding is `text/plain` then it could be kept). Sanitization should remove these elements.
+- `maction` should be replaced by its first child element.
+- `mphantom` should be removed.