Is your objection the identifier, or that there is a standard array, or the array size?
Why does it even exist? It adds 800KB of save data to any quest that includes it, it's not used or mentioned anywhere, and the name suggests it's garbage you forgot to delete.

...for -1 returns.
Eh, I guess. But that only happens if the inputs were invalid in the first place. I don't really like the idea of legitimizing script errors.

and CHAR_QUOTE is flat-out impossile, as the parser does not comprehend ''' as SINGLECHAR.
Huh, indeed it is. It should be possible to escape it ( '\'' ), but that doesn't seem to work.

Please specify on 'incorrect or nonstandard terms', and are the typos in the comments, or in the constants?
Mostly in the constants. Both, in some cases. I think this is everything:
130-187: There's an extra blank inserted. CHAR_QUOTE_LOW should be 130, and CHAR_0_SUPER should be 186. Everything in between is likewise off by one.
62: Generally said to be "greater than" rather than "more than," particularly in HTML, where it's encoded as >
160, 169, 196, 203, 207, 214, 228, 235, 239, 246, 252, 255: The mark is generally said to be a diaeresis rather than an umlaut. Doesn't matter much; they do look identical. But if they're going to stay as they are, "umlaut" is misspelled.
140, 156, 172: Angle quotes or guillemets, not mathematical symbols. » should be 187, but it's missing.
134: Ellipsis
135, 136: Dagger (the cross is U+271D)
141, 157, 198, 230: Ligature, not diphthong; also, 157 has OW instead of OE
174: Soft hyphen
181: Acute
209, 241: Enye
184, 247: Should have "MATH" variants to fit with predominantly American style

I have found that extended ASCII chars can be used, for allegro.log printing
Mostly, probably, but they're based on Windows-1252 encoding. 7F-A0 are different in Unicode and ISO-8859-1, so those are less likely to work correctly, especially on Mac or Linux.


Other things...

std.cfg:
typo: STD_EMULATE_EMGINE_COLLISION (it's unused, anyway)

std_constants.zh:
Irrelevant constants: NPCSF_*, BITDX_*, WARPFX_*, WARP_*, ITM_REQUIRE_*, maybe CB_*
Comments around NPCM_SPAWNFLICKER are wrong. 0x10 does indeed represent the flickering spawn animation, and the other NPCM_ constants are correct already.

Probably more. Lots of stuff to go through.