Umm. I am presuming it "correctly" impliments MXP, instead of what most muds do, which is test themselves against zMud/cMud, while entirely ignoring the specifications? lol
What do I means by this? Well, strictly speaking, the specs state "very clearly" that [ and ] must be escaped when stardard text. zMud and cMud, for some incomprehensible reason, ignore this part of Zugg's own specification, and quite happilly pass through anything they don't recognize as a valid tag. This "may" be intentional, to allow easier debugging, but in clients like Mushclient, which have their own error detection for MXP tags, invalid tags are "invalid", otherwise they can't be detected by the error system as an actual error. Needless to say, this has caused no end if irritation for some people trying to log into servers that don't bother to read specifications clearly, and instead just hack something together, which "works" with zMud/cMud.
Some attempt has been made by Nick Gammon, in talking with Zugg, to clear up this confusion over what the spec "should" say, and thus what should happen with invalid tags, but, at the moment, one of the two implimentations is wrong, and its not at all clear, based on the specification, which one. Nick thinks his is, since it follows the specification strictly, while Zugg's response has so far been.. well, not much of anything, other than a vague statement that, "Yeah, we should probably clear that up, eventually."
Its like trying to test a web page using either Firefox (strict standards) or IE prior to 7, with, "We just made up something that seems to work OK." All is well and good, until you try displaying one of those later pages in anything that "is" following the spec. lol