None of these are bugs, they're a reality of the mIRC parser.. that's why they were never "fixed". You really shouldn't be nitpicking about silly things like how mIRC reacts with code that violates the language syntax since the expected result is *UNDEFINED*. The invalid identifier warning you get is a convenience, not a requirement or guarantee. If you do something mIRC can't understand, that's your bug, not mIRC's.
As far as $1XYZ goes, that's a specific *feature* of the language, the same way the parser allows "//echo -a $mircdirSUBDIRECTORY" without using $+ for convenience. Not a bug.
