1) It would be a good idea to provide a server you are testing this on.
2) It's not a bug, rather a feature, 0 is invalid for the second parameter so mirc use a default value of 1.
3) This is probably intended behavior but I agree.
4) I reported a similar bug recently,
https://forums.mirc.com/ubbthreads.php/ubb/showflat/Number/234808/page/2#Post234808 but it seems to be intentional.
