We noticed that $gettok() does not actually like empty tokens.
//echo -ag $gettok(1#2#3#4#5#6#7,3,35)
3
//echo -ag $gettok(1##3##5##7,3,35)
5
OK, this MIGHT be correct in a way, as 5 is the third "non-empty" token. However, sometimes there are reasons to take the third token regardless of its contents, so in this case mIRC does not seem to provide a way.
I would consider it a bug, as it does not work as pronounced in the /help.