Yes, the identifiers you've mentioned aren't in the helpfile for a reason, but there is no reason for $nickmode not to be in there. It's not a bug per se, but this is the closest relevant forum for what he's posting.
Spelling mistakes, grammatical errors, and stupid comments are intentional.
Unreal IRCD and like IRCD's have modes qaohv o can't kick a and a cant kick q. the respective prefixes are ~&@%+ but alot of servers remove the ~& prefixes but qa still exist and have the same effect. if you are op and don't want to try and kick qa because you can't and modes ~& are removed it wont work. So using $nickmode is much more advantages to use when making such scripts. Wish I knew it existed sooner..
$leftwincid isn't documented either. Its function is pretty obvious if you know what $leftwin is (which is documented). Just thought I'd share this newly found identifier (as far as I know, it hasn't been mentioned in the past).