I noticed that for the ]KEYBOARD command, the comment symbol ⍝ appears in two places; on the C key, and on the \ key. I think, perhaps, that keeping it on the \ key and removing it from the C key makes sense for the following reason. The Z, X, C, and V keys are often mapped to the very convenient four characters each with a quad and one of the four arrow keys (up, down, right, left) which are very useful for keyed or component file IO.
I also, regretfully, noticed that I created my custom keyboard using the Dyalog standard rather than the standard used by GNU APL. Apparently, both the Dyalog standard, and the GNU APL standard differ from the IBM standard. Perhaps Standard is a poor word...