Not quite so. mirc can handle consecutive spaces, as long as the string isn't passed directly to a mirc /command. This means that identifiers and variables can handle those strings fine.
Take, for example, filenames. You think mirc can't play mp3s with double spaces, but this isn't true, unless you hardcode the filename in the script. This would be a very rare occasion; in most cases, to play mp3s, you'd have to use $sfile(), $findfile() or $read() (or another way to read from a playlist). In all these cases, you can use $shortfn($sfile()) or $findfile(dir,*.mp3,1).shortfn or $shortfn($read(file,n,N). If $sfile() or $read() returns a filename with double spaces, $shortfn() can process it fine. The script could even display the long filename with $longfn() but the handling of the file would be done with the short filename. Variables can store strings with multiple spaces as well. So even if you wanted to hardcode a long filename with multiple spaces in the script, you could put it in a variable (by typing it in Variables list) and use $shortfn(%variable) in the script.
My point, this lack of multiple spaces support in mirc might be annoying sometimes (the biggest annoyance is $1- in irc messages, just because you can't get around it in any simple way) but it's nowhere as bad as you think.
