Here are some very minor comments on SRFI 163.  (On a related note, I am
also studying SRFI 164 and hope to post some comments in a day or two.)

  - Ref. Draft #4 published: 2018/12/8

  - The examples of Rank-0 arrays and empty arrays are very useful.

  - format-array: The last example uses arr which isn't defined,
    although the context does indicate it should be the array from the
    first example.

  - Implementation: Kawa's format-array does not seem to accept the
    port/boolean second argument.  (Could be a problem in my setup,
    which uses a recent Kawa version from Gitlab.)

  - (re. Issue 2) format-array is very useful from a pragmatic
    perspective, and I hope it gets some standardization.  However,
    this SRFI may not be the best place for it.  Based on the
    discussion, it seems to me that the array-literals syntax itself
    is simple and noncontroversial but format-array is a bit of a
    rabbit hole, getting into format-strings and combinator-based
    formatting and so on.

  - Related to the above: I hope format-array and combinator-based
    formatting (SRFI 159) can work well together.  (I read John
    Cowan's suggestion but have not explored the issue enough to know
    if it suffices.)

  - What is the motivation for not making the Output part normative?
    In contrast to format-array, the situation here seems fairly
    simple.

  - (re. Issue 3) I like the idea of always requiring format-array's
    output to begin with a # character for the reason stated here.  (I
    don't think it will reduce the prettiness much either.)

Regards,

-chaw