Using a space doesn't work (even in identifiers or in quotes). Using a slash does work.
The primary reason I use $+ is for readability of code. Someone reading my code can tell how it would behave without any special knowledge of the quirky behavior of $*dir identifiers in mIRC. The fact that it also would not break if the quirky behavior was removed is just a bonus.
I don't see any reason why the ending slash would be removed from the response given by $*dir identifiers, so I don't really accommodate for that possibility.
