The list posted by Ouims is a list of $identifiers and $identifier.properties which don't trigger the "no such identifier" warning, which means you can't name your own aliases within those namespaces until mIRC is fixed to allow creating alias names in some of those areas. Most of the items in the list do not report the appended text, returning the same thing whether or not there is appended text (even if it's $null), so Khaled would probably be safe in fixing those identifiers. For example, $scriptlineAPPENDEDTEXT returns the script line number regardless whether or not there is appended text.
So far, I've identified only the following identifiers that alter the output to include the appended text:
$cd,$getdir,$logdir,$mididir,$mircdir,$mircexe,$mircini,$mp3dir,$script,$scriptdir,$wavedir
The above list is probably the only ones that need to preserve the existing behavior. The above identifiers are divided into those which return a folder-only and those who return folder\filename. The reason for appending text to the identifier is for changing c:\path\ into c:\path\filename.ext, and I don't see it being that useful for appending to a filename.ext.
I might have missed a few identifiers that only exist within narrow contexts. For example, $cd only works within ON SERV, where $cdABC appends ABC to the foldername returned by $cd. However from the editbox $cd and $cdABC both return $null.
