Telechat Review of draft-ietf-jmap-contacts-09
review-ietf-jmap-contacts-09-artart-telechat-bray-2024-05-18-00

Thanks for adding the Internationalization Considerations section, which
addresses the concern in my previous review that this issue needed more work. 
I have small issues:

1. There is a reference to "control characters" without any citation, and the
definition is not as obvious as one might think. A good reference is [UNICODE]
section 23.1, which may be summarized as "65 code points in the ranges
U+0000-U+001F ("C0 Controls") and U+0080-U+009F (“C1 Controls”), plus U+007F,
"DEL" 2. This section might benefit from a reference to RFC9413, which has a
thorough discussion of dealing with input data that is invalid for some reason.
3. There are 3 options when receiving a message with invalid characters: delete
them, replace them (Unicode provides U+FFFD for this purpose), or reject the
message. The draft mentions two of these but not the replacement option. Is it
never appropriate in the JMAP context?