ld16 is bugged

[ISSOtm]

This condition can never be met.

Unsure how to fix it.

[joeldipops]

rgbasm macro language can be very weird about brackets. To get it working I had to surround the two terms with brackets.
IF STRIN("\1", "[") == 1 && STRIN("\1", "]") == STRLEN("\1")
vs
IF (STRIN("\1", "[") == 1) && (STRIN("\1", "]") == STRLEN("\1"))

All good now:

MEH EQU $c000
ld16 [MEH], BC
ld16 BC, [$ff10]

becomes

ld A, B
ld [$c000], A
ld A, C
ld [$c001], A
ldh A, $ff10
ld B, A
ldh A, $ff11
ld C, A

[ISSOtm]

I hardly see how that could work, since this expects STRIN("\1", "[") to return two different values.