Merge pull request w3c#1529 from agl/i18n2

Tweaks to string handling section

index.bs

@@ -3998,9 +3998,9 @@ For example, in <a href="#fig-stringTruncation">figure <span class="figure-num-f
     <figcaption>The end of a UTF-8 encoded string showing the positions of different truncation boundaries.</figcaption>
 </figure>
 
-[=Conforming User Agents=] are responsible for ensuring that the authenticator behaviour observed by [=[RPS]=] conforms to this specification with respect to string handling. For example, if an authenticator is known to behave incorrectly when asked to store large strings, the user agent SHOULD perform the truncation for it in order to maintain the model from the point of view of the [=[RP]=]. User-agents that do this SHOULD truncate at [=grapheme clusters=].
+[=Conforming User Agents=] are responsible for ensuring that the authenticator behaviour observed by [=[RPS]=] conforms to this specification with respect to string handling. For example, if an authenticator is known to behave incorrectly when asked to store large strings, the user agent SHOULD perform the truncation for it in order to maintain the model from the point of view of the [=[RP]=]. User-agents that do this SHOULD truncate at [=grapheme cluster=] boundaries.
 
-Truncation based on UTF-8 sequences alone may cause a [=grapheme cluster=] to be truncated, but still valid [[UTR29]]. This could make the grapheme cluster render as a different valid glyph instead of removing the glyph entirely.
+Truncation based on UTF-8 sequences alone may cause a [=grapheme cluster=] to be truncated. This could make the grapheme cluster render as a different glyph, potentially changing the meaning of the string, instead of removing the glyph entirely.
 
 In addition to that, truncating on byte boundaries alone causes a known issue that user agents should be aware of: if the authenticator is using [[!FIDO-CTAP]] then future messages from the authenticator may contain invalid CBOR since the value is typed as a CBOR string and thus is required to be valid UTF-8. User agents are tasked with handling this to avoid burdening authenticators with understanding character encodings and Unicode character properties. Thus, when dealing with [=authenticators=], user agents SHOULD: