Which languages? In most languages I'm aware of you couldn't even get away with breaking comments using pipes.

Code:
Python:		# print "hello"; print "there"
Javascript:	// alert("hello"); alert("there");
C/C++:		// fputs("hello", stdout); fputs("there", stdout);
PHP:		// echo("hello"); echo("there");
Delphi:		// SomeCommand("hello"); SomeCommand("there");

All of those would ignore the second command after the semi-colon (their equivalent to a pipe).

While the fact that other languages do it doesn't necessarily mean mIRC should too, the fact is that it's not a case where the designers of those languages flipped a coin and ended up doing it that way - it's a purposeful design characteristic which benefits anyone who has to read or maintain code.

On the other hand, if for whatever reason Khaled decides that the current handling of pipes in comments should stay it would make sense for comments to respect braces aswell.

Spelling mistakes, grammatical errors, and stupid comments are intentional.