I'm not sure why you're checking $nick !ison $chan.
Since the newnick is $newnick, then $nick can't be on the channel, I haven't tested but your condition is certainly true all the time, I would use :
Code:
on !*:NICK:{
if ($newnick ison #your_channel) && ($hget(table,$nick)) {
hadd table $newnick $v1
hdel table $nick
 }
}

I've added the ! prefix, only trigger the event for other people than $me and check for $newnick ison #chan.
For the on quit event it's basically the same but since we know that the nick isn't there anymore, you have to check for $comchan on $nick :

Code:
on !*:quit:{
var %a = $comchan($nick,0)
while (%a) {
if ($comchan($nick,%a) == #your_channel) && ($hget(table,$nick)) {
 hdel table $nick
 break
  }
dec %a
 }
}

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